A833 early gearset in OD case?

Yes you can do that, however, the OD gear set uses a main shaft with a smaller diameter where the gears reside. You cannot put non-OD gears on the OD main shaft because the inside diameter is too large, so the main shaft has to match the gear set. Also, the OD case has the larger front bearing so if you order a rebuild kit make sure you get the larger bearing. There is an exception to the lack of interchange: the 22-tooth input gear from the 3.09 ratio 1st gear non-OD trans is the same as the 22-tooth OD version (this is true for the non-high helix OD gear set only, the high helix version uses a 24-tooth input shaft/gear).