Ours was a convertible. If we would have put the firewall bars in, all the stress from the flex would be on the door hinge pins and door latch pin. Bracing like that is always nice, but should never be required in threse types of cars. We had the splined sway bar.
There are some pictures on our site that will show the pie cut and rocker bracing
http://prodigycustoms.com/petes-camaro.asp