s4c final drive in y21 box?

[elvo]

hi guys, i know iv already asked if anyone has a final drive from an s4c box but i was just reading somethings on the net and now im not sure if the final drive will fit a y21 box.

i have a ek9 (s4c) diff and want to put this into the y21. iv had look and the amount of teeth on the final drive of the y21 is the same as the final drive on the s4c so im guessing i should be able to fit this along with the diff and have a y21 with a diff??

Any help on clearing this up would be much appriciated

thanks