While the 440 was a popular option in the RT, it wasn't the only engine available. You could also get a 1971 Challenger RT with:
* 383 cu in V8: This was the standard engine for the RT.
* 340 cu in V8: This was a less powerful, but still peppy option.
* 426 Hemi: This was the top-of-the-line engine, but very rare.
So, if you're looking for a 1971 Challenger RT with a 440, you'll need to do your research and find one that has it.