[ZOERA-SC7XX]

As far as the front GM brakes that are standard for ERA, You can buy single-piston aftermarket (several manufacturers make them) Stock Car Racing aluminum calipers that fit the stock mounting locations and Impala rotors to comply with track rules. Also, Hawk make several grades of high performance and racing pads that will fit these calipers. These calipers and pads stop/slow 3500 lb race cars running at race speeds without fading. The good news is they only cost about 100-150 bucks each. The may not be as pretty as the big buck set, but work almost as well as they do.
As for the Jag rear brakes, the rebuild kit and piston costs are cheap, and if you want, you can get vented rotors for the Jags (but need different calipers). Once again, if you don't intend to race your ERA, this stock setup is more than adequate.