Ok i had the idea that this would be an easy swap. I had a 76 someone had swaped in a nice 460 and had a 89 F350 4x4 that i gave a drink of water several years ago. I got the 74ish 460 finally in the truck and bolted to the 89 transmission and now the hang up is the exhaust headers. From all my searching it looks like the gaskets are the same for a 84 460 as it is a 74. Is that correct? Is there any headers out there that fit the 84 F350 chassis and if so would those fit the 89 chassis? the problem i am having is the huge crossmember that this truck has.

I know someone has to have done this swap before.

 

Frame is the same from '83 (first year of the 460 in this chassis) up into the '90's
So any 460 headers intended for a Bullnose truck *should* fit as long as 2wd/4x4, Manual/Automatic are known and followed.

***We did have a guy in the '80-'86 forum a few months back who installed Flowtech headers and they ended pointing directly at the tranny crossmember.
​​​​​​​He posted pics, and pics of the custom crossmember needed to avoid the collectors... but I wouldn't recommend that route.