Gearboxes for Troopies 78 series

I've been stumped by Toyota!! decided to change the Gearbox and Transfer case oils and so consulted the Gregorys and Ellerys workshop manual re quanities and type of oils reguired. Ellerys told me little other than quanities ie 70 series 4.9 litres for the gearbox and 2.7 for transmission ditto for the Gregorys but gave me the gradeof oil needed SAE 90. So of Up go and purchase a total of 7.5 litres of Penrite oil, dump the old oil from both unit then proceed to fill the gearbox first..pumping away then suddenly oil starts overflowing....what the! almost 3.0 litres put in Hmm clean up the spill and ponder the problem anyway decide my troopy does not have the H55f box as suggested... check the compliance plate and of course I have a R151 gearbox Hmm check Gergorys again, no R151 gearbox exists only H150F & H151F both for 80 series.. So I work it out that yes I put 2.7 litres of oil in gearbox that's consistant with the H150F/1F boxes So does anyone know what a R151 box is?? Its a Oct/99 build 1HZ non Turbo I've owned it since 2002 with 68K on the ODO ex Police Rescue Vehicle any clues anyone??