Chevrolet built 235,151 1968 Camaros. That means 940,604 bezels, 18,882 per week, were needed at two assembly plants for the 50-week production span.
It is entirely possible there was more than one supplier; those suppliers may have had more than one facility. The tooling to cast the bezels was produced by different tool shops; the engineering drawing for the part likely specified the part number was to appear on the part but may not have specified a location. So, each shop was free to put it where they wanted. High-volume tooling wears, likely replaced during the model year.
After casting, the bezels had to be plated. Last thing you want in supply chain is to be shipping parts all over the place for secondary operations. So, the casting/plating plants were probably close to Norwood and Van Nuys.
GMPD didn't necessarily source these from the original suppliers. Common for service parts to be made by shops that deal in small volumes.