1979 3+3 GMC Dually

[Puglia10]

Hey everyone. I was on here a while back with a 1980 c10, but the project was too big for me while I was in school and working.
Finally picked up a truck I’ve been trying to find for a long time. It’s a 1979 crew cab dually. It’s rust free from California (I’m in MA, everything is rusty) and it seems to be all or mostly original and unmolested.

My plans are pretty simple, being such a nice example I want to leave it mostly alone but clean it up (especially interior), fix the dents, AC, paint the fender etc. then lower it (maybe 6/8?) and put it on 22” semi wheels.

I’ll have some questions for sure, but figured it should go in the project section.
My first question is how to tell what’s original, what the truck came with, paint code, etc. can that all be accessed somewhere with the VIN? I want to check my rear end gears, make sure I get the right grille, etc. and find out any cool info - like what makes it a camper special and that kind of stuff.

On to the pics: