I am surprised that Morris's technical person did not suggest their AG90 which is what they describe as a classic gear oil. The EP90 contains the additives which are supposed to eat your bearings so that is definitely wrong. I haven't checked today but the AG90 was certainly still available last summer. Morris also do an AG140 and I think another, thicker still one. I was talking to the technical person about what to use in the rear axle of Madam's 1927 Standard and we discussed all these alternatives. Given the number of large gearboxes and back axles in old cars it would surprise me if these oils are no longer available.
If you buy online from Morris, remember to apply the Club discount code - available in the Members area.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), 54 4G Mk IV (project), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser.