There are a number of companies that can supply the needed parts. There are different makes for the positraction unit as well, depends on what brand you like.
Seems many of the bearing kits, gears, and even posi units are made by Yukon Gear.
I found a complete package for the B-O-P (Pontiac,Oldsmobile,Buick -all the same) 8.2" rear end. website is Welcome to Ron's Machining Service | Gaines, MI
- $675.00 USD plus shipping & this seems to be the best deal to me. Just click on the link.
Eaton and Auburn are 2 good names in positraction units, but $400 -$500 USD just for it. Then you have to buy the gears and all tour bearings, so it can get very expensive when you buy each piece at a time and then ship each item. Buying a complete package can often be your best choice.
Richmond & Motive Gears seem to offer ring & pinion gears sets.
Quick Performance is another website that offers the Yukon brand of parts for the 8.2" rear. Other suppliers also have the parts, but it is all about how much you want to pay for it.
I like Timken brand bearings and National Seals if I am just buying individual parts -both were used on factory produced autos over the years. I am sure other makes will work just as well, but I am not too familiar with some of them, so do not know of their quality.
Hope that helps.