'74 Duster Bumper Mounting issues

I've got a 1974 Duster, it came with two different bumpers, a beat up and twisted '74 bumper and a near perfect '75 one, I can't get the '75 bumper to mount up properly it seems to be about a half inch wider on both sides. I looked for the '75 mounting brackets but couldn't find them, I did find the '70-'71 brackets though, would the '75 bumper mount up to the '70-'71 brackets?

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