Don’t let the “I wanna make it ‘mine’, so I’m gonna change ‘this’, add ‘that’, and completely remove ‘those’” mentality come into play...AT ALL!
In other words, don’t buy one with an AX15 (a popular 5 speed transmission swap) with thoughts of switching it out to a 4R70W [popular, but overrated (IMHO) automatic transmission swap]. Or, buy one with a 5 1/2” suspension lift with plans to drop it to 3 1/2”.
This happens far too often. You are paying for custom work, only to have to pay MORE to undo that custom work. Then, you guessed it...you get to pay for more custom work to “build it your way”. I can’t tell you how much evidence of changed work that I have had to cut off of Broncos only to add more changes. That adds up fast!
I tell my customers: shop labor is the same whether I am fabbing custom mounts, or shining the tires. Don’t spend the same dollar twice...it always costs more than the first time you spent it.
Also, learn to recognize the differences between the ‘66, and all other years; the 67-68, and other years; the changes made in ‘71, ‘73, and ‘76; and the peculiarities of the ‘77.
If you arm yourself with that, you can buy the closest thing to what you want, the first time. I have built several customers’ “second” or “third” Bronco when they didn’t buy right the first (or second) time.
Finally, if all else fails, build it “new”, from scratch! You can literally build the Bronco of your dreams...and there are several ways to get there.