You'll have to check the rearends, I've read somewhere (again don't remember where) that in either late 83, or 84 they began putting 8.8" in the rear of the bronco. I too wouldn't touch the 400 engine. If time and money permits wait and get a 460, then build it crazy sick and twisted! The 79 would probably be easier to build and has the arguably more desired solid front axle. Keep the 79 and build it to the hilt. my .01 cent. Would've given .02 cents but my bronco's got me broke!