Rear end question
There’s a good chance it’s an 8 3/4, but for gears it could have almost anything. Nothing between 2.76 and 3.55 from the factory would be all that surprising.
But remember we’re talking about a 47 year old car. It could have anything in there at this point. Especially with an 8 3/4, it’s easy enough to just swap out the whole 3rd member.