bumper interchange?

67-72 valiant bumpers are the same as 70-72 duster. you MAY be able to convert the fronts by removing all the shock absorber junk and using mounts from an earlier car. not sure if the bolt holes on your car are in the right place, but you could fab up new holes easily enough.
The rears aren't even close, I don't think they would work, nor do I think they would look good... theres just too much difference in the rear body lines/shape for it to look natural, but thats my opinion.