Dodge Challenger Rallye 340
For 1972 the options lists (both for performance and appearance/convenience items) had been drastically cut back. The convertible version, most interior upgrades options, 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 Rallye series. Engine choices were down to three: 225 cu in slant-6, the 318 cu in V-8, and the maximum power 340 cu in V-8. All three were detuned to lower compression ratios in order to run on lead-free gas, and the horsepower ratings lowered to reflect the more accurate Society of Automotive Engineers (SAE) net hp calculations. Each engine could be mated to a 3-speed manual or automatic transmission, while the 340 could also be hooked up to 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. The only 1972 convertibles which exist are actually 1971 models with the 1972 front end (grille, lights, etc.) and rear end (tail lights and their panel). These were specially built for TV programs such as "Mod Squad".
The only way to ascertain a 'real' 1972 Challenger convertible 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). A cigarette lighter was standard.
Source: Wikipedia, 2012