Z,
I've always had good luck with both
synthetic and petroleum gear lubes, in the 75w-90 range. The main thing to remember is with petroleum based lubes, you need to add the friction modifier in the posi rears. With synthetics, it's usually not necessary. Brands are more of a personal choice than anything. I think all the name brands offer a quality product. Now, having said all that, I use Red Line in all my rears(oh, that really didn't sound good, did it?)
Dave