Welcome Zach! This is a great place to learn and share. If you aren't aware, there is a show in Spartanburg this January and another one in Simpsonville in May. Both have a decent turnout for models and a swap meet area to pick up more kits!!
While that is true, I would be willing to bet that they would sell a boat load of these kits with a 4wd option! I have the front suspension from the Super Stones kit to make one of mine a 4wd, but am lazy enough to just buy a kit that already has the parts in it! LOL!
To have a mid-70's GMC grille, you would need to make your own as the one from the '84 GMC pickup is totally different and nowhere near close. You would be better off starting with the Chevy grille from that kit and re-working it to a GMC.
Go to the Modelroundup website, I think they carry the Gofer brand of decals and if I remember correctly, they had some pinstripe decals. Bandit Resins also had some pinstripe decals, not sure if they still offer them.