Sounds like you have it under control now. GREAT!
I'm sorry I did not see this thread earlier as I just replaced my pinion seal and cover gasket on my Corp. 12- bolt.
The pinion seal I used is a:
NATIONAL (Federal-Mogul) 8460N
Do like the other guys said....marking the pinion nut relation to the driveshaft yolk, and the driveshaft yolk to the rear axle....and counting the threads for good measure.
But if you get overly concerned about the torque on the pinion nut:
Get an INCH-LB 'beam style' torque wrench, jack the rear wheels off the ground, remove the brake drums (to relieve all resistance on the axles), and check to see that it takes 15 to 20 INCH-LBS to cause the pinion to turn. Remember...what to look for here is 'resistance'.
My manual says that 15 inch-lbs is spec (if new bearings and crush sleeve are installed), but if you are not replacing bearings and crush sleeve that 20 is recommended to reset pre-load and compensate for worn bearings and sleeve.
I filled my differential with Royal Purple...and so far it all is working like a charm. No clunking, whining, or anything else wierd.
Plus...no big oily spot on the driveway!
I hope I've explained this right....