I recently installed a 6.1L hemi in the wife's '71 Cuda.
It basically sounds like a Ram 2500 with a 5.7 Hemi and an exhaust albeit a bit louder since it goes through long tube TTi headers and no cat converters.
The engine it replaced, a 360Magnum 395HP crate engine, sounded nastier but not to the wife's liking as far as ease of driveability, no a/c, blah blah blah.
So now she has something closer to 450hp, smoothe idle, a/c, 130amp generator (whick will power a nice sound system and power windows) and teh ability to just jump in, turn the key and immediately hit the a/c button