The bumper fillers show to be available from www.replica-plastics.com Theirs are fiberglass; originals are urethane.
The lower door panels can be painted rather than dyed if recoloring is all that is needed. Parts are made of polypropylene and require a special primer. Instructions are in the Fisher Body Manual. Typical damage appears where the outer textured layer comes off and leaves a chalky surface behind. Replacement would be required in that case.
By the mid-'80s GM was selling these panels only in black. These had to be painted to match. GM part nos are: right - 9852288, left - 9852289. These numbers were used on a majority of Buick/Olds/Pontiac full-size 2-doors from '71-76. So finding used panels in good condition is a possibility. There's one on eBay now (Item 173380135719).
Reproduction parts for the lower panels do not seem to be out there. Looks like not too much activity yet on GM full-size interiors from the '70s. Found some vendors offering door panels for '71-72 Rivieras with base trim, but not clear if lower panels were included.
Last edited by TODD; 07-11-2018 at 03:26 PM.
Reason: Add BOP reference
What has been, can be again. (Bob Wills, 1942)