Troy,
Wish that I could speak to the ERA FIA specifically, but my ERA was a 427 and it is a different set-up. If your FIA is anything like my Superformance FIA it is a pain getting back there. I had to open mine up to build the roll cage. I had to remove the seats, transmission tunnel and the rear bulkhead to get at the roll bar. On my car there is also a bolt through the forward facing leg near the role bar and another one underneath the car at the frame.
This is what mine looked like.
Good luck, it is a pain and you have to do a lot of wiggling and maneuvering even with everything out to get it out and then back in.
Jim