Just thought I'd kick in my newbie two cents. If you go original, it's all original parts. If you replace original parts with equivalent parts from something else, it's stock. If you use different parts replacing the original, it's modified, and if you buy a fiberglass body and a tubular frame, it's a kit car. Going by those standards, you're talking about a modified (hot rod) truck in my book. As long as you bought the original truck, it's an old truck. I'm sure a lot of the guys on here have bought fiberglass parts, stronger engines, better brakes, or something that wasn't even thought of when their trucks were built, so do whatever you will enjoy the most.
Also, anybody can open a book or go to a museum to see an original truck.
