Carriers:
Auburn HP series posi unit part # 542018.
This is the entry level posi for our 8.5" 10 bolt rear ends with 28 spline axles. Typically good till you get into the 500 rear wheel hp range. However, I've seen cars with 450 rear wheel hp wear this unit out with frequent track visits with slicks. It's a good stock replacement carrier and your factory 3.42 gear set will bolt right up.
The best Auburn posi unit is their Pro Series part # 542050.
This unit is good for up to 750 rear wheel hp. (Even though some have pushed it well past this level) It has a beefier clutch pack and can take more abuse than the standard HP series unit. It is also for 28 spline axles and your factory gear will bolt up.
Anything more power wise, (800+) and I'd recommend either an Eaton unit. or a Detroit Locker.
Installation kit:
Raytech Deluxe kit # 3003K contains everything you would need to do the job right, including axle bearings, carrier bearings, shims, seals, everything.
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Ratech 3003K - Ratech Deluxe Ring and Pinion Kits - summitracing.com
Rear differential cover options:
For far out factor, Trans Dapt has a clear diff cover part #8402.
However, I would recommend upgrading the rear diff cover with one of TA Performances' cast aluminum covers. Either part # TA_V1807, or part # 1807.
TA_V1807 with the Buick logo.
TA Performance Products Inc.
1807 with the carrier bearing cap, pre load torque screws.
TA Performance Products Inc.
With all of these parts in hand, a few bottles of diff fluid and posi additive, a competant shop should be able to get you setup and rolling quickly.
Hope this helps.
Patrick