[randy500]

I think this is the deal on the rear bumper brackets...

The catalogs are wrong.

There are 2 styles of inner brackets shown in the pictures above.
The one with the top cut away and the thick metal reinforcement welded on is for 69-71 blazers. The cut away is needed to clear the last body rubber mount that is under the frame in that location. 72 blazers do not need this bracket because the frame was modified so that no inner bracket was needed. It’s very difficult to install a bumper bracket on a blazer because the forward hole is blocked by the gas tank so in 72 they fixed the clearance problem with the frame re design.

As seen in the above picture the regular bracket fits a 67 short wheel base leaf spring truck and all other trucks except blazers 69-71 4wd and 2wd. And all 4 wd tucks have the longer bracket with longer bolt hole spacing.
I think thE rear bolt hole is common to all the brackets which spaces the bracket from the frame.

I think the leaf spring frames on short wheel base trucks one of the rivets interferes with the bracket, drill a hole for clearance if required.