Why a V8. Be easier to Hot Rod a 6 cyl., & keep it closer to stock looking. This would eliminate alot of unseen problems. I've owned pretty close to thirty COE's through the years, & seen quite a few V8's stuffed into original frames. Most that did it, said if they had it to do over, they would have either put the engine behind the cab, or put the cab on a later chassis already V8 equipped. Remember if you put a V8, in that original frame, you'll have to find a better suited rear axle also.