Hey all, this is very interesting indeed...It may be possible to upgrade the entire rear end (with a bit of work) and get an LSD and disc brakes for about the same as the hard to find LSD's cost. I imagine the Mazda design would be lightweight, too-Not big and bulky like a mustang, etc.
According to this site, the track of the Mazda is 55.1 in.
www.geocities.com/MotorCity/Speedway/3734/firstgen.html
The track on a roadster (from R&T) is 47.1 in.
So, you will need to remove some length from each side of the axle...
Also, the site says that the final drive ratio is 4.076:1 for the GSL-SE and 3.9:1 for the non GSL-SE.
Hmmm...TR