Sleeping 2 would be tough because those crappy mopar seats don't recline.
The "six way seat" option is the only thing that's make these cars driveable. Any AMC from the same era rides, drives, handles better and is more comfortable than an equivalent mopar. A GM car rides and drives better than that.
Also, the idea that Superbirds lasted on dealer lots into '71 is really no big deal. Lots of '70 model performance cars sat on dealer lots into '71 and later. Our '70 440-6 cuda sold in April '71 for $3400 ($1000 less than sticker).
Superbirds were just more visible on the lots than the others.