In the WHEELCOVER THREAD
you mentioned the Ray Miller book, "Camaro! Chevy's Classy Chassis" and brought up a good point regarding the timeline of that book. April of 1981 was the first printing, which means that the research and pictures were done in 1980 and perhaps even earlier. This means that the 68's referenced were approximately 12 years old. I looked at the RS Grilles of the two cars that still had the original California black plates, and noted the color of the grille -vs- the license plate number. Here's what I got:
License VIW 548 (Page 98 through 105) Black Grille (appears to be chromed on page 100 but I believe that to be due to the lighting.)
License WBH 171 (Page 96) Black Grille
Both of these cars are "San Diego County" cars (City Chevrolet, located in San Diego, and Weseloh Chevrolet, Located in Carlsbad), and going by the License Plate Numbers, both of these cars are late 68 models as well. "V" and "W" License Plates were mid 68 releases for San Diego County. (My first 68, which I bought in February 1976 from the original owner, was also a "W" issue and it was a June (Los Angeles) built car. And now that I think of it, this car (also a SS/RS) had the black grille because I remember other 68 RS owners telling me it was wrong at the time!!
Anyway, it's staring to appear that the late 68 cars may have received the black grille. Of course, either or both of these cars in the book may have had their grilles changed at some point, so this data could be skewed. But if not, it's just more evidence to support Steve's theory.
Oh yeah, my current car is also a Los Angeles built car, built in 05D. Les? Steve? Are your cars Norwood or Los Angeles?