R12 vs 134a

You guys aren't getting what I meant.
As far as evap and condenser I was wondering if they changed things like fins per inch, spacing between tubes etc
and in the drier... I was wondering if they changed the whatever in the bag within for the different types of freon. I think I have the basic how to figured out/ but right now, I know that I have some parts left to locate/ like mount brackets and such. and maybe a dash out of a 80s truck that had factory AC to begin with. (Preferably marroon)
I think I got a guy that I can get the dash from, just need to make the drive up there if he hasn't sold it yet. Just asking these sort of questions while I'm in the parts gathering phase/ so I make sure I get the right ones.
I do have enough R12 stockpiled to run it on but once that's gone where do I get more? So I'm setting it up by for 134 from the get go.