[Three Peaks]

Frank,
The originals and Superformance have different mounting points and I'm quite sure the trunk is slightly different so the measurements between the two may not make much difference other than the overall height.

A suggestion you may try is to cut some pieces of 1 1/4" EMT in the approximate lengths for the back brace and try to trial fit the pieces together to see where all the pieces will end up to make it all fit. Then you can take all the information and put together the pieces to form the roll bar. You may need to custom fab a rear trunk mount, cut and reweld the rear brace mount on the roll bar, and cut the roll bars to length to make it all fit.
This would be easier to explain and show in person, but this is the process I had to go through to make the roll bars for my Cobra built on one of Roger Bollick's original style chassis.

Good luck with the project. I'd like to see how it comes out when it's done.

Bob