The Challenger and Barracuda Restoration Guide (and any other book I've ever seen about restoring Mopars) is RIDDLED with errors! Do not believe everything you read, the cars and parts themselves are the best guides concerning originallity.
AAR grills (and headlight buckets) were MOLDED in black plastic, they were not painted at all.
All other 1970 (and 71) Cuda grills were molded in gray plastic (The shade of gray varied, I've seen shades from light gray to a darker gray, but not nearly as dark as black) and painted argent silver.
Only Gran Coupes and AAR grills recieved the chromed plastic rectangular bolt in grill trim pieces, Cuda's recieved a multiple piece red stripe bolt in plastic stripe, base Barracudas recieved no inserts at all. I have seen RARE exceptions to these trim options but believe they were simply factory mistakes (for example, my real 1970 Cuda was missing the red grill stripe from the factory).
All Argent painted grills (all non AAR's) were painted the same shade of textured silver agrent paint
All 1970 Cuda/Barracuda Grills (including AAR) recieved a bolt in chrome plated "plymouth" emblem in the inset area near the far end of drivers side
The best match to OEM piant I've seen is sold by Mike at All trim Specialties in Oregon. Roger Gibson Restorations also carries a close match. All others I've seen sold by several well known vendors are not even close!