friends of mine are on a budget and restoring an original 60k 74 road runner. white interior and it was pretty chalky and rough. they asked me if i could do anything with the parts (all the plastic in the interior as well as medal a pillar trim and fabric on the panels)
i own a specialty media blasting company so said i would try it. anything too aggressive will destroy the grain obviously so i went with vapor blasting (cabinet based water/ #10 glass bead mix) other than filling my cabinet up with old chalky plastic it worked very well. retained the grain and brought the panels back from the dead. perfect? nope, but very nice for stuff that should have been replaced. Door panel upholstery come out the best looking like a NOS part when finished. (material was in great shape)
if you have anyone local you could have them try vapor. try on the backside first or a spot you cant see once installed to be safe.

i have great luck with mopar plastics and vapor. might be an option