An '87 is now a 20 year-old truck and likely to need new bushings and possibly other parts in the suspension anyway. If you are going to need to disasemble to replace the parts anyway, why not do that work to update the older frame?
You won't have to change the wheelbase or modify body mounts, and since the same suspension design was availble from '63 through '87 newer designs are easily adapted.
Separating the engine choice from the suspension choice lets you choose your motor and suspension based on the best pieces.
