[Gunner]

It would seem to be very much a case of reinventing the wheel. The original Jag IRS is superb; the ERA-reengineered rear is at least as good, 50 pounds lighter, repositions the brakes for cooling and serviceability, and is highly tweakable.

I doubt you could save very much money by building your own or adapting something else, and I strongly doubt you could do better in performance.

But I suppose you could adapt a Vette or BMW rear setup if you really wanted to.