Tucking factory 74 bumpers

I have a '75 Valiant, and the rubber behind the bumper (front and rear) is looking pretty sorry. Is it possible to tuck these, and if so are you just tossing that elastomer stuff?
I have (I believe) a '73 Valiant, and I'm hoping the bumpers will be slightly narrower than the factory '75's. There was a thread on here where a guy narrowed his bumpers, and they looked awesome!