If you have a pinion seal then your truck has been molested as there’s no such thing with a torque tube setup. If the stock rear is there the bearings and seals are available from places like BC Bearing, Kinecor, Commercial Bearing, etc. cheaper than the vendors and here’s the numbers:
Rear axle seals: CRC 18695
Rear axle bearings: National R1502CL
As for an online source, here ya go but they have no stock:
http://www.chevsofthe40s.com/detail/6277/Chevrolet_REAR_AXLE_BEARING_SEAL.html