Classic/Antique Car Repair: Pinion nut torque specification, pinion bearings, torque specification

Question
I would like to know what is the torque specification of the pinion nut on the rear differential of a 1961 Bel Air as i need to replace the pinion seal?

Answer
REPLACE PINION SEAL.

The procedure that I use to replace a pinion seal while the differential is in the car is as follows. With a center punch I mark the nut and the pinion shaft so that I have alignment marks when replacing the nut. Then remove the nut counting the number of turn. Remove and replace the flange and seal and re install the nut counting turns. Finally align the nut with the marks and you have returned the nut and adjustment to exactly where it was before the repairs. I have used this practice for 50 years after being shown it by my great uncle who was a field engineer for the old Peerless Motor Car Company.
The torque listed in the factory repair proceedure is used when replacing the crush collar with a new one that is located between the two pinion bearings. This proceedure will reset the preload right were is was. Brad