67 Chevy C-10 rebuild?

I just bought this truck from this guy who knew nothing about it. He said it had a 383 stroker but I think it's actually a 350. Now what I need to know is what kind of transmission and what type of rear end are in this truck. Now It may be safe to ume that both are not original. My question is how to find out what type of and what gears and what type of rear end are in this truck. Can anyone help me out? I just got a 4.10 posi quoted at $1200. Anyone know if there are serial numbers of some sort on these? The is a 3 speed auto, but that's pretty much all I know.