For the 1972 model year, the options lists (both for performance and appearance/convenience items) had been drastically cut back. The convertible version (though a sun-roof was made available), most interior upgrade options (in particular leather seats), comfort/convenience items (in particular power windows and power seats), and all the big-block engine options were gone. The R/T series was replaced by the Challenger Rallye series. The Rallye model featured four simulated vents on the front fenders, from which exited matte black strobe tape stripes. Engine choices were down to three: the slant-6, V8, and a V8 that was equipped with a 4-barrel carburetor, dual exhausts, as well as a performance-oriented camshaft and heads. All three engines were detuned to lower compression ratios in order to run on lead-free gasoline, and the horsepower ratings were lowered to reflect the more accurate Society of Automotive Engineers (SAE) net horsepower calculations. Each engine could be mated to a 3-speed manual or automatic transmission, while the 340 could also be equipped with a 4-speed manual if so ordered. The performance axle ratios were also gone except for a 3.55 sure grip which could only be had with the 340 and the heavy-duty suspension. The 1972 models also received a new grille that extended beneath the front bumper, as well as new rear tail-lights. Toward the end of the 1971 model year, a few convertibles were made with the 1972 front end (grille, lights, etc.) and rear end (tail lights and their panel). The only way to ascertain these 1972 Challenger convertibles is to look at its fender tag. On the code line which gives the dealer order number, that number will start with an "R", which designates "Special Meaning" (in this case, a TV 'special promotions' car).