[special-K]

There are and there aren't numbers matching with these trucks, just not in the muscle car sense. The suffix code on the truck block Denotes the vehicle it came in, just not the exact vehicle. Every truck came with a specifically numbered block that is correct for it's configuration. Any other code means non-orginal engine.

I'm having a hard time figuring what is important to you. I got the impression you bought the truck because it's all original and are disappointed to find it isn't because of the engine. By that I'd say get it right. Find a motor with the suffix code for your year and configuration. Example: TDL means '72 307 2bbl 135hp auto C10 & C20. Now that engine could also be an '80 350 4bbl 155hp from a van.

Then you are pondering all these other options and that makes me wonder what original matters. Are you at a threshold between keeping/getting back to all original (except repaint in original color) or stepping in a new direction? If so, no one can tell you. It's up to you to do what suits your needs.