I need to correct my prior input on phosphate and priming 1st Gen Camaro bodies. The bodies were primed after the 7-stage phosphate coating process.
Here is an except from the Norwood assembly sequence article covering the Fisher Body Paint Shop Operations:
"The Paint Shop is broken down into phosphate, prime, sealing, and color departments; the body was suspended from an overhead conveyor with hooks at the firewall and at the ends of the rear frame rails through the phosphate system, and was transferred to a steel carrying truck before the prime system that carried it through the rest of the Paint Shop and through the Trim Shop.
Phosphate System: The raw body shell passed through a seven-stage phosphate system, where it went through a series of enclosed high-pressure hot spray stages where it was washed to remove all the oils and debris from stamping, welding, brazing, soldering, and grinding operations, then the body was coated with a hot iron phosphate solution which "etched" the metal and provided "teeth" for paint adhesion. The final stage was a de-ionized hot water rinse and blow-off, followed by a drying oven on the way to the prime booth.
Prime System: In the first prime booth, the entire body, inside and out, was manually sprayed with primer, and confined areas subject to corrosion were given a second coat of heavier primer material; this prime coat was then baked at 390F for 30 minutes. In the second prime booth, the instrument panel and rear of the shelf area (and the upper door and quarter areas of 1967-68 models) were painted interior color, and another coat of air-dry flash primer was sprayed from the belt line down. The interior color areas were masked, and the entire outer body was sprayed with gray primer-surfacer and the body was baked again at 285F for 45 minutes. The cowl vent panel was hung in the side window opening on wire hooks all the way through the paint process."
My Camaro and vetteskip Camaro were built during the same time period with gray primer floorboards. I supposed it was possible, but perhaps not likely, the Fisher Body Plant at Norwood switch between gray and low sheen black primer on the floorboards, but then as it has been said in our hobby, nothing is absolute about how our GM cars were originally built and anomalies or deviations to the process have been found.