If it was mine I'd put an SAE50 TO-4 in it, maybe with some anti-squeal additive if there are wet brakes in it.
However to give things a bit of context the circumstances I'm usually in are that most of the fleet is specced to run TO-4 oil in the rear end, final drives, swing drives, etc, anyway. Having an EP gear oil as well means another tank on the lube truck, another storage tank, another line system in the shop, etc, etc. So if 80+% of gear oil compartments are running TO-4 it makes sense to run the rest on the same oil if at all possible. I can only speak for myself, but the results of going from EP to TO-4 were excellent. Judging by his comments on HEF, I think heymcall has had similar experience.