My ITR trans is in need of some TLC. And being that I have a turbo, Id like to extend the gearing some and am looking into possibly swapping some gearing for either GSR or LS gears. For instance, is it possible to just swap 1, 2, and 5th gears from a GSR or LS into an ITR tranny? Are the spacers, synchros, etc different in a GSR or LS compared to an ITR? I dont want to buy a GSR or LS gear set and have them not work in my ITR trans. Since my trans is in need of an overhaul, Id rather rebuild this one with different gearing than just buy a whole new/used GSR or LS trans.

Ive done some searching, there is a lot of information on the gear ratios of each, but its hard to find info on compatibility between the gears in different trannys.