Broncos that came with a stock external tire carrier have additional supports behind the sheet metal that trucks with internal carriers don't have. If you don't add interior support, the carrier will rip the sheet metal. Some have had trouble with large spares damaging the tailgate even with the stock supports. The strongest solution seems to be a rear bumper with a tire carrier built on it. Several of us have added the stock type spare carrier, with various results. If you add a stock external carrier, you'll need to add support inside both the tailgate & the fender.
I added an external carrier to my 90. It has been ok so far. I carry a 33" BFG m/t on an aluminum rim, so it is not as heavy as some spares. I wheel it, but I'm not crazy with it. No jumping. I can see some flex in the quarter panel when the spare is all the way open. I am always careful when it's opened. It seems solid & tight when it's closed. It is somewhat misaligned in that the rubber block at the bottom hits before the latch. I think it keeps it tighter & may prevent damage. I also kept the interior spare carrier. It's pretty much out of the way with no spare it, gives me something to lash to, & makes it easy to carry 2 spares on the trail (Some guy named Tom told me early on I should always have 2 spares :toothless).
For the tailgate, you probably want to use the stock support for inside the tailgate. It's just way too easy to install the stock brace to even consider making one. It has to tie into the structure inside of the tailgate to distribute the load. It can be unbolted from one truck & bolted into the next. If you add a carrier to a Bronco that never had one, use that support.
Here's a pic of the tailgate support (Pic borrowed from Dustball). The top is at the left. You can see the 3 holes for the latch. The other holes mount to the structure inside of the tailgate.
There is also a support inside the fender, but it can't be removed from a good truck without a lot of work/damage. It's better to get that part from a truck that's being parted out, or to make a new one. If you use the stock fender support, you may have to cut it to fit it into place.
My internal fender supports are made from 3/16 plate, bent to fit. They are each bent twice with 2 flats that contact the fender at the bolt holes, & a center portion that doesn't contact around the curve. The edges are ground round, to try to keep from them punching through. They don't connect to each other or to the existing internal bracing like the stock brace does, but it would be stronger if they did. I may still modify them to do so.
It's easier to make the supports to fit the shape & hole pattern of the carrier hinge brackets. The hinges are the same shape as the fender, & it's much simpler to work with the hinges on the bench than trying to bend the steel to match the truck.
Here is a sideways view of the stock support inside the rear fender from Mickaila's Bronco build.
And a shot through the taillight opening of one of my homebuilt braces (It's getting rusty in there, it should have been painted. Even inside of the quarter panel in California :doh0715. You can see how it isn't formed to the fender at the curve, but takes a straight line across.Here is an overall view, again, ITS UP SIDE DOWN, as you can see the top portion of the panel (where the soft top sits) on the ground presently:
Be aware that the design of the latch changed (I think the break is between 89 & 90, but I'm not sure). The older ones have a long release lever & sort of a hook strike, while the newer ones have a short release handle & a latch mechanism similar to the doors. Make sure that the strike you buy matches your carrier. :brownbag
The fender is a different shape for 78-79s, so be sure to use the matching hinge brackets. I have heard that the carriers themselves will swap between 78-79s & 80-96s if you use the correct hinge brackets, but don't know that personally.
They also went from 2 holes mounting the latch to 3 at some point. The 2 & 3 hole parts may work with each other, but you might have to drill a 3rd hole & add a nut behind. My internal tailgate brace had only 2 holes. They matched 2 of the strike holes, & I drilled the 3rd.
Here's an earlier strike (89 & before?):
Somewhere there's a pic of the later strike (90 & later?) When I find it I'll add it.
Be aware that the stock internal carrier is designed to hold the tire at an angle so that the top of the tire leans toward the window. I had trouble with mine coming loose until I realized that the tire was supposed to slant. Now it stays tight.I wish mine was on the out side.its on the inside an i hate it. the tire all way's works its way off the tire holder drives me nuts. plus does not give me much room in the back of my truck what so ever. Butt have to carry a spare right.