It was a Factory Five Roadster, which is designed to have a "donor" car of a 5.0 Mustang's innards. Basically, they fabricate the body, mounts, frame, dash, etc and you use the engine, tranny, wheels, electronics, etc from the 'stang. The kit comes with coilovers, but most racers change them. Back then, the kit only came in a live axle set-up, but now you can get one with Independent Rear Suspension.
HP and Torque are a bit better than stock, because the kit comes with a K&N cone filter and no cats (straight true side pipes), but the tubular steel chassis and fiberglass body shave 1000-1500 lbs off of the 'stang. It's a beast - and quite fun.