I would go with an 85W-140 conventional gear lube.
I had done this by mistake the first time around, and in my case it was Delo ESI 85-140. Has been fabulous in that nefarious Ford 8.8, Those are especially leaky if you have prolonged highway runs. I had that after a few coast-to-coast road-trips (although the unit had more than 200k miles by then).
Mr Zeng helped me to clear my head then, thank you. Now I pay attention to ISO numbers, apparently that is what engineers go by.