66 or 67 B Body. spring pads are > 1" difference from stock. the slop in the bushings and chassis allow a direct bolt in without modifying the axle. You need to remove the leaf spring isolators too, i used my stock F body main leaf and added the spring pack from a 67 BB B body with a new through bolt

here's my build little info on the rear though https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2116859/1.html

15x10 3.5" backspace 295 50 15 tires.