now that is something i didnt look at, on the gearboxes theres studs sticking out from the nuts and the mounts slide on and tighten with nuts over the top

are you saying the spacing on the gearbox nuts and studs sticking out is different? if thats the case you might well of hit the nail right on the head mate? all i can say is i had both boxes next to eachother but possibly just possibly i didnt notice