what fluid to run in rearend for the 87 gn stock 10 bolts w spline axles?

[hemi]

what fluid to run in stock rearend 10 bolt with spline axles? thanks for any help.
also car has under drive pulley on it... dont have the belt any one know the number for the belt?

 

[87gninpa]

I just run parts store 80W-90 and a bottle of GM Posi Lube. 205k on the stock parts and still going strong, no need for synthetic IMO.

 

[SS/GN]

Dino 80/90,I like the stuff with the additive already in.Quaker state is what I have on the shelf. .No synthetics,and do not put the additive in with the brands that are already mixed

Kevin

 

[Boost231]

80w/90 no additives

 

[hemi]

thanks every one