There is no such thing as a 72 RT Challenger. The RT was stopped in 71. The confusion always lies in the VIN. Because 72 Rallye's start with JS, most people think it's an RT because 70/71 RT's started with JS. It's real simple, the Rallye was a 'model' in 72 (therefore part of the VIN) and an 'option' in 73 and 74 (listed on the fender tag). Car lots and flippers, etc usually list them as "RT" cars, but Mopar guys like myself, who actually care about these cars, know the difference.
Similar confusion with the 72 Rallye Chargers. No RT's after 71, but because the Rallye is similar to the 71 RT, people get mixed up. The 71 RT is a WS code in the VIN, and Rallyes are WH or WL.
Another pet peeve...72-74 GTX. 71 VIN is RS. Last year, period. The confusion is the 440. GTX only had 426 and 440. Roadrunners with 440 engines are sometimes 'coined' as GTX cars, because in 74 (not sure about 73) the GTX will appear on the hood of 440 RR's. Sometimes called the 'GTX option'. It's still an RM code Roadrunner.
Basically, all 'S' code cars (GTX and RT) are stopped after 71, EXCEPT the 72 Challenger Rallye. Not sure why Chrysler did this, it sure creates confusion! (maybe they thought the Rallye would take over where the RT left off???).
I just truly like and appreciate Mopars....