ERA Sells a couple
Gen 1
Gen II
I have an 03 Mustang Cobra and have had the IRS out of the car. It is a monster compared to a Cobra roadster
Pillaged photo - 99-04 Cobra
An ERA is going to fit - IMO Fords system would be misapplied (I think a T56 in a roadster is misapplied also so take it with a grain).
I have the cradle, control arms, uprights, anti roll bar, and brakes for a Gen 1 that came out of my FIA. Six pin hubs and wheels also.
You would need to supply the XJ6 differential and shocks (ERA has assembly instructions) and of course location and attachment to your chassis.
chr