Yeah, you can still get parts for it, you just have to search for them. I know AMain has them. And I'm sure there are others. If you do in fact need a diff gear,
CLICK HERE. It's the stock gear that loves to melt out the center lmao. Oh the good days.
And yes, it seems that there is something slipping really bad in there.
As for those screws, I have found a left handed drill bit to be best. It spins CCW and when it grabs really good, will back that screw out with ease. Then, just go to your LHS, or order than off the internet and replace the ones that are bad. Here is a really good place to make sure you have quality allen drivers.
Man, I think I'm more excited about this truck than you are lmao. Takes me back to the good ole days.