Welcome to FABO Jesse! I am in CA so trying to help with any of the big stuff would be expensive to ship. The parts you are looking for are out there but they are going to be a little pricey. As for the rearend, I would take measurements to verify that it is a b-body version. Even if it were, since the car is no longer #s matchng I wouldn't worry about it. Again, if it is a b-body rearend, I am curious to see if they moved the perches in or not and what backspacing are on the wheels (sometimes used to compensate for the slightly longer b-body rear.
As for the front bench, I would really like to see pics of it and the entire interior. Does it have a blue two tone pattern? Depending on which one you have, there is a possibility that you could reupholster it but pics would help. Also, the car's build date would determine if it came with headrests or not.
Good luck on your project.