Stick with same era truck 300-6 ,5.0 5.8.
The 4.6 take different transmissions,motor mounts (If you found them for a 80-96 F150). Fuel systems . Drive shaft would have to be made. And they feed off speed sensor in rear .
with complete harness from newer EFI F150 87-92 For the ecu if you have manual OK if not get one that(87- 92 none electric auto or manual trans)and some repining of you truck to make stuff work .
Basically would have to replace tank (s) to EFI type and install pumps wiring .
Easy way is to find a whole truck to sawp stuff from as you will save on trips to wreckers
