As mentioned before, these brakes are designed for 74 thru 81 Camaro's. These cars are A LOT heavier than the Cobra's and work very well for street applications. These are the same brakes we used on a 1980's Imsa Kelly Challenge car with race pads. If you can slide the car under full braking, you have more than enough brakes. I just found this out just the other day when someone pulled out right in front of me. Yes, the brake upgrade is nice and under certain circumstances is a must. But, it's nothing you will ever encounter on the street. My car brakes are very nice and it is well balanced. If anything I wish it had more rear brake BUT I like the way the ERA's package works. One thing you will find is that ERA's are very well sorted out. Their products work well and are engineered that way. I wouldn't worry so much about the Chevy aspect of it. The calipers are $35.00 all day long at any parts dept. and there is less moving parts to worry about! It has just one very large piston. Trust me it works!
If your concerned about the Chevy parts don't forget about the Subaru steering rack, Jaguar rear end, Volkswagen turn signal switch, Triumph steering column, Falcon shifter boot, MGB headlights, Corvette radiator, Corvette expansion tank(FIA), and etc. A Cobra has an incredible assortment of parts from all kinds of different manufactures even on the "originals". Are you sure a "FIA" wouldn't be better for you?
Good luck with the search. Regards, Matt