"I am thinking of replacing the bushings and oil seal the old fashion GM way, but really do not know where to find the correct rear bushing and oil seal."
"While I am at it I was thinking of changing out the pinion and ring gear so I can Cruz at highway speeds."
Jim,
SWEET's advice is excellent. If you are going to get the 3.55 R&P, you will not need to worry about how to get out the old bushing and seal. You will knock them out from the inside (instructions come with the R&P kit). SWEET also has an excellent photo-log of the installation.
There is no need for the "correct bushing and seal". Use the Oakie bushing that comes with the R&P parts. As SWEET suggests, also buy the installation kit.
Call Patrick's directly and ask if he gives a Stovebolt discount. Tell him you have heard good things about him on this discussion board.