The grill shell bolts up exactly the same and uses all the original mounting points. The difference is the headlight mounting brackets, which need to be changed and lowered. New holes need to be drilled in the rad support, after lights are lined up with the grill inserts. The corner pieces which tie the top of the rad support, inner fender and fender together are different, but the originals will work if you drill new holes. No big deal. The marker/directional light sockets are also different and need to be rewired. I like the 73-75 inserts better than the 76 and up ones. Here is the difference>>>
The ebay link above is nice because it comes with everything you need. I had to go hunting for my headlight brackets at the junker.
I bought a parts Bronco from a guy who used to be on here alot and it came with the package. Eric Toblaski, alot of the guys will remember him. I got the 460, 1-ton axles, the bumper and alot of other great parts. Let me search the members list and I'll see if he has been around lately. I think I still have his cell number too, so I'll call and see if he remembers where he got the bumper. I can check the paperwork and receipts he gave me too.
Kenny, what year did they use the amber lenses? Was that the later models? Also on the headlight buckets, 1st off mount the shell then set the buckets in place with the grill inserts and mark where they need to be drilled? I am in the process of doing this swap on my 79. I need the F O R D letters if anyone has a set they don't need.
I believe the 73 to 75s where clear lenses with amber bulbs and the 76 to 79 had amber lenses with clear bulbs. As far as marking the holes, I did it just like you described. I set the bracket in there loosely, installed the inserts with two or three screws, centered the bracket and marked 3 of the 4 holes. The 4th hole was difficult to reach so I just marked 3 and was able to get the fourth after the insert was removed. If your using the 76 to 79 inserts it's going to be harder to mark the holes because of the design of the insert. Just get someone to help position and hold the bracket while you hold and position the insert. Remove the insert and mark away. I suggest drilling the holes oversize and using the original mounting harware. It will give you a little room for adjustment if you need it.