Diff oil. Your recommendations please ?

After 8 years of building, the time has come to fire up my Speedster project for the first time.
I have my head around most things but I need recommendations on a good diff/rear axle, oil. Please consider that it has modern inner and outer bearings and seals, a modern pinion bearing and modern roller thrust bearings…no bronze.
A lot of products that are available in the USofA aren’t available here, so I’m not really looking for a brand, rather, the specifications of the lubricant.
I look forward to your recommendations,
Thanks & Cheers,

Rob, just about any 85W - 120 or SAE 90W is fine. I use whatever is on sale.

Thanks Royce.
Much appreciated.

Please don’t whap me, but…

I run 600W (and change it regularly) in mine… not only because Ford and Ruckstell said so, but because it’s formulated NOT to attack the brass and bronze in the bushings. And ya know what? After running 85-140 in the Ruckstell and dealing with popping, grinding, and insecure engagement, when I went to what Henry recommended, regardless of what the great internet minds told me… it quieted down and acted like a 2 speed rear end.

YMMV but if the Manufacturer says run XXX, then run XXX.

And for those who say Hall Scott said to run 20W20 in their axles… in the 1920’s… I want to see where 20W20 or equaly thin oil was ADVERTISED back then to run in Hypoid Planetary Differentials… . Because they DESIGNED that thing to run on what Henry specified, and he specifies that evil, ugly, and surprisingly effective 600W steam oil, and surprisingly… when you follow the manufacturer’s recommendations, it works.