gear oil recommendation needed

[Slamtry]

Can anybody recommend an appropriate gear oil for an un-modded 5-speed
Classic? It does not have to be synthetic. Just needs to be right for the
car. I need to buy some as I must replace the axles this w/e and it seems
I will have to drain/partially drain the tranny. I have not been able to
find any GL4, 75/90 oil anywhere. FWIW, I am located in Santa Monica, CA.

Dan