Frames [Archive] - FSB Forums

: Frames

07-13-2010, 04:16 PM
trying to help a buddy, are the frames the same size and thickness for 1970-1979 F-150, F-250, F-350?

he is wants to make his F-150 a F-350....

Thanks Fert

07-13-2010, 06:48 PM
I'm sure someone knows, and not trying to "flame", but why are you asking this on a forum about Broncos that were only built on the F-150 frame starting in '78?

Check out this forum for more F-series truck based questions:

07-13-2010, 10:29 PM
i figured there was enough super smart Ford people here who might know :thumbup

07-14-2010, 11:41 AM

Here ya go; Some info for your pal

Technical Drawings and Schematics - Section D
Frame, Body and Related Components:

Frame (Typical)
1965-1972 F100, F250 (4x2)
1966-1972 F100 (4x4)
1967-1972 F250 (4x4)
1964-1972 F100-F250 (4x2), F100 (4x4)
1964-1972 F250 (4x2), F350
see more @

"... One of the more frequently-asked questions from owners of truck owners involves a body swap of their '67-'72 body onto a '73-'79 chassis. This article will explore the similarities and differences between the two.
NOTE: All references to 'bumpside' and 'dentside' trucks in this article refer to the differences in the body-side contours. The '67-'72 bumpside trucks have a convex contour (a 'bump') running down the body's beltline, whereas the 'dentside' trucks have a concave contour (a 'dent'), as pictured in Fig. 1 at right.

Fig. 1 - The '67-'72 truck on the left is a 'bumpside' and the '73-'79 truck on the right is a 'dentside', both for obvious reasons.

Swapping the bumpside body onto a dentside chassis is often a inexpensive and less labor-intensive method (comparatively speaking) of upgrading an older truck to power steering and power disc brakes. There are also several other advantages, such as:
Allowing you to have a rear-mounted fuel tank (depending on application)
Getting a wider differential housing for slightly-enhanced stability
For F100/F150 trucks with a 9" Ford rearend, the pumpkins usually had a stronger 31-spline setup, as opposed to the 28-spline used in earlier trucks.
Let's explore these in more detail:
When Ford introduced the Twin I-beam front suspension in 1965, the front track width increased by several inches over the previous Mono-Beam solid axle setup. However, they continued to use the same-width rear differential, resulting in a mismatch between the front and rear track widths of the bumpside-era trucks. However, this was corrected beginning with the 1973 2WD and some 4WD models. While the frame remained basically the same from the rear of the cab forward, everything from the back of the cab rearward was widened out to 38", an increase of 4". The following chart shows the widths of the rear framerails of various models:

'67-'72 2WD/4WD narrow (34") - see note 1
'73-'79 2WD wide (38")
'73-'79 F100 4WD wide (38")
'73-'77 F250 4WD narrow(34")
'77-'79 F250 4WD wide (38")
'73-'79 F350 2WD Super Camper Special narrow(34")
Note 1: I'm not entirely sure how far back that goes, as 34" wide was an SAE standard for all trucks back then.

In their 1973 promotional literature, Ford stated the wider frame spacing, in conjunction with the new long 2" wide leaf springs, improved road stability. With the redesigned frame came a new 4"-wider rear differential housing, which finally enabled the rear wheels to track directly behind the front wheels. Obviously, the leaf-spring mounting pads on the newer differential were also spaced 4" farther apart on the axle tubes.
FIG. 2 - SOURCE: 1973 Ford promotional brochure
The wider framerail spacing also allowed for a rear-mounted fuel tank in most models that "is mounted within the protection of the husky frame siderails under the rear of the pickup bed just above the spare tire". This replaced the in-cab tank, which in turn gave the driver more room inside the cab and some storage space behind the seat.
The frame redesign didn't stop with simply widening out the rear was also stretched back 2", increasing the standard LWB wheelbase from 131" to 133", and the SWB wheelbase from 115" to 117", which in turn made the pickup bed 2" longer as well. (Ford had described the bumpside SWB box as a 6-foot box, but now referred to the dentside version as a 6-foot box, while continuing to refer to the LWB version an 8-foot box.)..."
more @

IMPORTANT: There's a rumor floating around that Ford redesigned the front crossmember for the '77 through '79 2WD trucks, which also meant the engine perches had to be redesigned, so these trucks couldn't be used as engine perch donors for earlier trucks. However, while there were redesigns on stands in '77, it wasn't due to a change in the crossmember. (In fact, '79 6-cylinder trucks use a D4TZ (left) and a C5TZ (right) stand. That means one stand never changed from inception!) The '79 trucks use a D6TZ-5019-B frame front crossmember which is also the replacement for '73-'78 and fits all F100/F150/F250 and F350 2WD with Twin I-beams.

- The FE stands were revised in '74 and have D4TZ numbers
- The 351M/400/small-block stands were revised in '77 (D7TZ numbers) but are used as the replacement for all 73-79 Twin I-beam trucks
- The right-hand 6-cylinder stand for '74 was a D4TZ but was replaced in '75 by the C6TZ right-hand, and then in '78 both 6-cylinder stands were redesigned and had D8TZ numbers.

Ford discontinued the 390 V8 in the F-100 in 1975 and both the 360 and 390 in all light-duty trucks by 1976....except in CA, where you couldn’t get a 390 in an F100 after '73. Therefore, to install an FE into a '76-'79 truck you simply use the I6 stands (Fig. 6) when doing this swap.

more @
Suggest you ask this Q w/more details such as what year F 150 he has now, parts your pal has on-hand for the conversion and/or ask what he needs for it;
ask @

BurntOrange had a "Standard Catalog of 4x4s" book that did list a lot of Bronco & F series info.

he wrtoe here; Frame Strength & Dimensions in 80-96; "...This got me thinking and I just found my Standard Catalog of 4x4s book. It has info on every model year domestic 4x4. It doesn't really specifically talk about frame differences from year to year, but it does have a Chassis Features section for each Bronco year. Here's what it has: (1980-1985) Separate body and frame, box-section welded frame. 3.95 in. section modulus (1986) Separate body and frame, single channel, 5 cross members, welded frame. 3.66 in. section modulus. Maximum side rail section: 6.95 x 2.12 x 0.170 in. (1987-1989) Separate body and frame, single channel, 5 cross members, welded frame, 36,000 psi steel. 4.27 in. section modulus. Maximum side rail section: 7.01 x 2.12 x 0.202 in. (1990-1992) same as 87-89 but also notes low carbon steel (1993-1996) Separate body and frame, single channel, 5 cross members, welded frame, 3.66 in. section modulus. Maximum side rail section: 6.95 x 2.12 x 0.170 in. low carbon steel..."
Source: by BurntOrange at FSB (
I haven't seen him here in quite awhile tho; but maybe you can use the internal e mail option to ask him for the info

Standard Catalog of 4X4'S, 1945-2000 (Standard Catalog of 4 X 4s) [Paperback] (
Robert C. Ackerson (Author)

= ========================
I had some notes on this in my old site at CC;
Mark wrote;
The 77 & older F-250 4wd high boys had I think a 1.5" narrower frame from behind the cab to the rear bumper.
The 78-79 F-250 had the wider frame like 74-79 F-150's, 2wd and 4wd.
Also of note is that the commerical cab and chassis f-350 duallys all had the narrow frame and spring up into the mid eighties and utilized the narrow spring perch Dana 70's. The desireable Dana 70 is the 78-79 f-350 super cab 2wd wide spring perch.
Jason wrote; " have a '78 F250. I believe the frame is the same width as the 1/2 tons; Just measured my frame. Outside to outside on the front measures 34 inches. Just like BobbyB's 1/2 ton. So the 3/4 ton 4x4 frame is the same width

For engine, etc Codes see the FORD PICKUP TRUCK RED BOOK, 1946-93 Model Year Including Bronco, Ranger, etc. Overview w/Changes, Some Years w/Pics, GVW, Body, Engine, Transmission & Rear Axle Codes, Exterior Body & Interior Trim Color Codes, MSRP, Optional Equipment & Prices; Appendix A contains Overviews & Examples of; Warranty & Rating Plates, Build Date Stamp, Casting Dates & Manufacturing dates, Sheet Metal Date Codes, District Codes (DSOs), Assembly Plant Codes & Production Date Codes. Also includes F-SERIES TRUCK PRODUCTION FIGURES for 1946-79 including Bronco for 78-79
Source: by Peter C. Sessler via
in my site @

Suggest using; Right Click on url; open in new window..and so on for each section and year bec all are slow to load here; mainly bec of lousy Comcast cable issues.


07-15-2010, 08:52 PM

07-16-2010, 04:19 PM
I'd like to see what your pal ends-up doing