'74's had rear shock bumpers, but had standard front bumpers. My '74 Duster had standard brackets up front, and so did the '74 Dart I parted out. Not only that, but my '74 Duster is a pretty "late" '74, with a production date of June 1974. '75 was the first year for front mounted shock bumpers.
One thing my '74 Duster does have is both sets of mounting bolts for the front bumpers. It has the captured nuts in the frame for both the standard mounting brackets as well as the later shock mounted bumpers. Earlier car's didn't have captured nut for the shock mount bumpers, and 75+ cars didn't have the captured nut for the earlier standard mount bumpers. Lucky on my part, as that was something I didn't know when I bought my '74 Duster. Good thing too, because otherwise I would have had to come up with a way to mount my '71 style front bumper when I converted it to '71 Demon bodywork.
As far as collapsing the shock mounts and tucking the rear bumpers up closer to the car goes, it won't work very well. Not because you can't defeat the shock bumpers, you can, but because the bumper is significantly wider than the back of the car. The rubber filler takes care of the gap because the bumper sticks out so far, but it also tapers back into the body. If you put the later style bumper right up against the body, the ends will stick out by more than a inch past the width of the quarters on each side. I looked at tucking in the stock bumper on my '74 before I realized it was actually easier to just use the earlier non-shock mounted bumper and brackets.
