Most of the hypoid gear oils you buy by the quart are okay for limited slip. You need to read on the container. If it does not say so, go get some that does.

At the auto supply they usually have it by the quart, and most all I've read the label on, were for limited slip.

You can get an additive for limited slip at your chevy dealer if you can't find any that is designated for limited slip.

Good luck,