Wich rear diff...?
 

Which year rx7 did the drifting rear diff come with. I have the chance to get a rear diff off a 89 gxl. my car is an 88 so would it fit.

lol, there is no "drifting" rear diff.

If you're talking about the clutch-type rear diff, look for an 86-88 GXL or an 88 GTU.