Bevel gear and rear diff. fluid type

[MilehighV70XC]

Replacing the bevel gear and rear diff oil this weekend. I have searched all over and have a couple questions. It seems that any full synthetic GL-5 (sever service) will work for the bevel gear and rear diff. I don't have time to get to a dealership. Will Mobile1 be just fine? Also, do the bevel gear and rear diff take the same fluid? Both fluids are a 75w-90w, correct? So I would put the M1 in the bevel gear and diff?
I looked all over the owners manual and it says nothing about what type and weight to put in both cases.
Sorry for the noob question just don't want to mess anything up.

[Ozark Lee]

I used Royal Purple 75W90 GL5 on my bevel gear while I had it out for the engine change. No strange noises or anything from it but I don't have a prop shaft in the car at the moment. The Mobil 1 should be just fine as well for both the bevel gear and the differential.

...Lee