Keep in mind that some of the 70 Montes(not sure about the 71-72 Montes)got 12 bolts and I believe that all the 70-72 Montes had Chevy rear ends which used C-clips to retain the axles vs the more desireable 71-72 Olds/Buicks 8.5 A-body rear ends which utilised bolt in axles.