Not much as far as a EASY bolt in swap. If you have anything but a 455 you have the 10 bolt 8.2 rear if you have 455 motor you have a 9 3/8 Buick rear. Electra might bolt in clean...You can try other full size Pontiac and Olds (88, 98, bonneville, catalina, executive) rears from 68-70 But I am sure you will have some spring perch and control arm geometry slight differences. Worth a look