Just got my supra diff kit incl. 3.73 diff for £450 (brand new second hand). Going to be doing the Weir kit mod which increases the preload on the clutch pack, allowing it to lock up harder and keep one wheel from spinning.
The kit is $45 or $75 depending on intended use of the diff; street or track.

Imo the rear mount from MK and the different style diff covers available to avoid cracking the Supra diff housing, are really not designed properly.
All reaction forces are directed completely wrong into the standard cosworth style mount, so I will design my own rear mount.

Look at how the diffs are mounted in the supra mk3 subframe to take up the bending moment of both axis.