What grade gear oil do ineed for a lister sr3 gearbox please?

If it is an original Lister mechanical gearbox it should be E.P.90 (the same in the reduction gear-if fitted) If it is a hydraulic box,most of them use the same oil as the engine,(P.R.M.-Hurth-T.M.P.) except Borg Warner,which uses power steering fluid.(the red stuff)