A Cobra is Ford Special Vehicle Team's (SVT) version of the Mustang. From '93-95, the 5.0 engines were equipped with iron GT40 heads, a different cam, a GT40 based intake, 1.7 roller rockers, 24lb injectors, and a different computer as well. The standard Cobra T5 also came equipped with a steel bearing retainer from the factory, versus the aluminum on the standard 5.0 HO Mustangs. In '93, the Cobra had a different rear spoiler, taillights, rear bumper, side skirts, and the front bumper had an open grille, along with 17" wheels and 4 wheel disk brakes. In '95, Ford put a 351 and Tremec 3550 transmission in the Cobra R. From '96-'04, the Cobra was equipped with a DOHC 4.6L rated anywhere from 305-390HP depending on the year, with the '03-'04 being supercharged for the 390HP rating. In '99, the Cobra was first equipped with independent rear
suspension, however it was ditched in '03 in favor of a solid rear axle to handle the higher horsepower and torque of the supercharged engine. The Cobra has also only been available with a manual transmission. I can't think of anything else off the top of my head, so other than that, someone else will have to answer for ya. The Saleen question looks like it had been answered pretty well and without getting too much into detail, they had both cosmetic and performance mods performed by Saleen, and were available for sale at Ford dealers. Hope that helps!