Nearly any GL5 is fine. Do you know if your rear axle has the factory Tracloc limited slip differential? If you do just make sure the back of the gear lube bottle says something like 'Compatible with limited slip differentials' which says it has the required friction modifier. Most GL5 lubes have that. Some aftermarket lockers/LSDs specifically advise not to run a friction modifier.
The exact viscosity is not critical. For most casual driving a lower viscosity like 75w-90 or 80W-90 is fine. For towing or more extreme duty something a little heavier like an 85W-140 would be fine.
I have the original window sticker, I'll review that first. I believe is all original. Thanks for the input Jerry.


