[swedishandgerman]

I would recommend a high pressure gear oil in the rear axle, GL-5 (Hypoid) and I would be more concerned about the pressure rating (GL rating) rather than the viscosity.

GL rating is based on how much pressure is exerted between the gear teeth as the gears are under load.

With reference to viscosity, 80 was recommended, but I don't know whether multi-grade gear oils were available back then. I like the idea of 80/90 for good viscosity in a range of temperatures.

There were different gaskets available so I would speak to the people at Brookhouse to makes sure you're getting the correct one.

PS: You're right! There are no stupid questions on this forum!