would a 91 T2 LSD or a S4 LSD fit on a 91 GXL and how

 

I think you can only do that if you use the whole T2 drivetrain, since the diffs and drive shafts are different (and using a different one requires using a T2 tranny and clutch).

 

your gxl has lsd... but no, it wont fit right in.. halfshafts and driveshaft flange are different.

'lil bitch.

 

quote from faq:

"Did my 2nd Gen RX-7 come with a Limited Slip Differential?
Only the following FCs had a LSD from the factory:
86-88 GXL
87-91 T2
88 GTU
89-90 GTUs (however not the 89-90 GTU)
It is also rumored that a few rare 91 coupes with both the A (upgraded the interior trim, added a power sunroof, tilt steering wheel, cruise control, and 4 piston front disc brakes and vented single piston rear brakes) and the B package (leather seating, a CD player, and rear cargo cover) came with a LSD, but you should note that Mazda denies that any FC other than the T2 came with a LSD in 91). You can also tell by looking at the differential as there will be a LSD tag on S4 cars with a LSD."

the s4 diff Should work, though im not 100%, but not the tII

 

no such thing as a 91 GXL anyway

 

^yeah, that too^