Need help with Bumper Guards please

I have a 70 Duster 340 and bought bumper guards for it. The front have 2 mounting holes, the top is not used. The rear guard doesnt align with the bumper bolt.
They are the correct ones from the pics I have from other 70-72 Duster's.
So can anyone please help me as to why the mount on the guard doesnt align with the bumper bolt on the rear bumper?
If you have a 70-72 Duster with bumper guards, please look at yours and get back to me asap.
Thanks,
Ed