Oil filler for gearbox is right next to the clutch linkage with the level marked on the side of the filler.
Dipstick is for the rear axle and the filler is behind the seat, between the lift arms.
You have a choice with the oil. It can either be SAE90W, SAE30W or SAE20/30W. Ford recommended all three for transmission and hydraulics from 1952 to the end of production in the Fordson Major.
A Super Major or Super Major 5000 from 1962 to 1964 should have SAE30W or SAE20/30W not SAE90W.
Do not use any EP or Hypoid rated gear oils.
4.5 British Gallons ... Gearbox
9 British Gallons ... Rear axle/Hydraulics.