i have just purchased a LSD out of a 90 model MX83 Cressida on the advice that this center will fit straight into my diff housing, if not i have an MX83 i can put it in but id rather some added topspeed on the supra. has anyone heard of/done this sort of thing?
Definitely will not fit. The MX83 Cressida's differential has the same internals as the MA70 Supra's differential- and that means that it is larger than the MA60 diff. The MA60 diff is 7.5 inches, right? The MA70 diff is 8 or 8.5 inches.
Correct. The MA61 has an F series centre (7.5") while the MX83 and MA70 have a G series centre (8"). It is theoretically possible to put a G series diff and carrier in a Mk2, but you're talking lots of custom work there.