B is for Bumpers

Have purchased a 1975 Duster Custom and doing it the right way. Problem is both bumpers are rotten to the core (play on words). Have researched to see if a 72 or earlier would work and basically found out that there is a body change in the rear and front so this is out of the question. I am wanting to make this an almost everyday driver and would like to hear some ideas or whatevers to help me out. Would a fiberglass hold up to everyday things? I know that there is really no structural support so how about somei deas.
There are three main components to your bumpers. The outer that you see, the inner that is most of the structure and the absorber mounts.
If its 'rusted to the core'. are they all gone?
Don't know if fiberglass is available. If so, would like to know what they use for mounts since not like older style that just had mount brackets. Usually the point of fiberglass is to save weight, but most of the weight is in the other parts not the outer. Eliminating all the inner' parts would cut a LOT of weight.
My outers don't look great, but are still functional till I find better. Had rust holes in the absorbers and parts of the mount flanges gone. Front inner was OK, but back inner looked like swiss cheese from catching salt. I found the inner parts I needed from other members here. Will probably get the chrome replated eventually.