On my 74 "FrankenDuster", I used 67-72 front bumper and a 73 rear. The car came with the same "shock absorber" types so I did the following:
REAR: New AMD bumper with stock brackets. I welded a .120 wall steel plate over the HUGE hole in the panel that the shock absorber used to pass through. Holes were drilled for the early bumper mounts and the bumper was fitted like stock.
FRONT: Used 1970 bumper and brackets. The frame rails had the HUGE threaded hole for the shock absorber type bracket, but also had the two holes for traditional mounts. The two holes had no threaded nuts, so I made a sheet metal plate with nuts welded to it and slipped it in through the end of the frame rail, then plug welded the plate through 4 5/16" holes that I drilled in each frame rail.
The early bumpers are smaller, lighter and just look better to me.