It's never been a styling issue. It's always been an engine issue. When it comes to muscle cars, engine drives values more than anything, and 1972 is the commonly-accepted end of the muscle car era. When the Black Monday impacts started hitting in 1988, the cycle went 70-72 BB E body, 68-72 BB B body, 70-72 SB E body (340, AAR, TA), and then all E body. The 68-72 SB B Body market didn't do much of anything until prices reached a point in the early 90s when enough parts vendors and reproducers showed up to make cloning profitable. And all that time, the Mopar mags were touting 73-74 were gonna be big, but it was not to be. Same deal with the 66-67 cars.
It's funny what you said about the front end. I always disliked the 71-72 fronts, and loved the 73-74, but I've read article after article over the decades that attack the 73-74 designs because of the size of the bumpers. I always thought they were more ticked at the laws that forced the change in designs than the design itself, but that's just me.
