You install some in-floor SFC's in a Foxbody, and you will quickly gain an appretiation for just how crappy a chassis a Foxbody is. It's floorboards, and material between the subframes is about .040" thick.(probably 19 gauge sheetmetal) Even the front subframes are about .040" thick. I don't see how the chassis supports the weight of the car. I didn't install Griggs SFC's, but I installed some in-floor SFC's that extend into the rear subframes(which are over .100" BTW) and tied them into some Steeda FLSFC's. I need to find a way to connect my cars cage with the SFC's, but the cage is installed wierd. It connects to the big hump where the rear seat is instead on to the actual floor of the car. BTW if you like the IRS then you will really like it after Bruces bushings go on. Huge improvement.