The 1972 Charger introduced a new "Rallye" option to replace the R/T version. The SE was differentiated from other 1972 Chargers by a unique formal roof treatment and hidden headlights. The 383 engine was replaced with a lower compression 4-barrel 400, while the 440 engine were still available, rated at net 280 hp (209 kW; 284 PS) rating instead of the previous 350 hp (261 kW; 355 PS) gross values. The ratings went down as the net horsepower measure was more realistic. Also beginning in 1972, all engines featured hardened valve seats to permit the use of regular leaded or unleaded gasoline rather than leaded premium fuel as in past years due to tighter emissions regulations. Though the 440+6 (designating a triple 2-barrel carb setup and 310 bhp (231 kW; 314 PS) was listed in the early 1972 sales literature, it was found in the August 1971 testing that this engine would not meet the new and more stringent 1972 emissions laws, although some early Dodge literature (August 1971 press) stated that this engine was available for 1972, and a few (six is the accepted number) factory installed six-pack Chargers were built, the engine was dropped out of production by September 1971.
The low-compression 4-barrel 440 Magnum 280 hp (209 kW; 284 PS) with a 4-barrel carburetor then became the top engine, and the optional Pistol-Grip 4-speed Hurst manual shifter could be coupled to the 340, 400, and 440 Magnum engines. The Ramcharger hood scoop was discontinued, as well as elimination of optional lower geared performance rear axle ratios and extra heavy duty suspensions. It was also the final year for the Dana 60 differential, and was available only in combination with the 440/4 speed, heavy duty suspension, and the 3.54:1 rear axle ratio.
Source: Wikipedia (original)