what oil 3.5 v8 and oil for gearbox

hi me mate has a 1961 series II and is looking to do all the oils diffs gearbox (manual with red and yellow knob ) and engine which is a 3.5 v8 from a sd1 1976-1987 can anyone tell me the best oils to use thanks

used to use a high quality turbo diesel oil in high mileage V8s kept them quiet and very clean changed the oil every 3k plus the temp range of the oil is good Jai

It says either 15W/50 or 20W - 50 for the engine and carb dashpots in my Rover SD1 workshop manual. The main gearbox transfer box (provided they are series selectable 4wd type), axles and steering box take EP90. Nice engine that - They are more powerfull than the Range Rover and Land Rover carb V8s because they have a higher compression ratio, bigger valves and more efficient SU carbs. If it doesn't already have them then Range Rover 3.9 V9 exhaust manifolds and down pipes will get a bit more power out of it.