The 6.5L with no turbo using the 6.2L Intake and exhaust should drop right in.. Take a look around, there was a 6.5L N/A Engine available as a goodwrench crate replacement for the 6.2L I have seen a few.
As for How much for a project truck.. Kind of depends on what it needs, and what kind of shape it's in. Long bed 2WD will be cheaper, short beds and 4x4 will cost more.
I just bought a 79 project truck with an Olds 5.7L Diesel (and hydro boost brakes) for $250. Granted I paid $400 to have it hauled 500 miles to me but, it was worth it, the engine runs great truck drives straight, and best of all aside from the bed floor being rusted through from having a plastic bed liner and the bottoms of the doors. The body is rock solid. The underside is rust free and still has shiney paint.
Has Collision Damage on the left front, the paint is shot and it has surface rust in spots but it's solid.
I think it's well worth $650 considering I paid $800 for my 85 and it needed a tranny. Had no A/C and a Trashed interior. Just about every body panel except the doors and bed floor have rust perforation.. Guess where those are going..
