'60's and '70's trucks have different frame widths compared to '80- '99
You're looking at cutting and rewelding spring perches and shock mounts at the very least.
Imo you're much better off with a 9" 5 on 5.5.
3.50 & 3.73 were pretty popular, but you can find almost any ratio for them.
Edit: Don't get me wrong, I've got nothing against the 8.8, and Ford did make them far beyond '87
There was a 3.54 in the right pattern.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.