What made A bodies non-popular

yeah that was the so called facts but the 440 was pushing well over 400 and wasnt the hemi pushing close to 500? i say that cause i think on rcc they would take rv and truck 440 and clean them up new intake 4bbl headers duals, would clear 350 to 375. and chargers were cammed and i dont remeber wat all they did. so 390 horse for a 440 is kinda a fib i think