Hello all. Are the final drive units on the following all the same?

-85-87 - trx250 fourtrax (4 stroke)
-85-87 - 250sx and ES

I need one for the '85 TRX and cannot find one at decent price. I checked the part #'s on partsfish and they are the same, but I've been fooled before. At the one parts place I stopped at he had 2 entire rear ends from a couple 'mystery machines' (as he put it). The one was identical in every regard, and the other one was so similar, but where the trans axle shaft bolts up to the final drive was different dimensions. He wanted WAY too much $$$ for it. More than I paid for the entire bike X 2. I think I'll have better luck if I know for sure that the sx's and ex's and trx's are all the same. There is a lot more of the trikes around here than this quad. Any help would be appreciated. Thanks