Interesting topic and one that I have been doing research on for a number of years, and try to photo document when I find them.
I have seen body build sequence numbers on survivor 1st Gen Camaros that included the same number on the firewall and written on the inside surface of the lower front valance panel as a final subassembly of the entire front fenders and grill. At the Norwood assembly plant, the body from the firewall rearward was near completed by Fisher body, while the the front sheet metal subassembly was completed on Chevrolet's final assembly side of overall build process. According to the book Echoes of Norwood, a great book about the history of the plant, it explains Norwood at some point in time starting writing a body sequence number on the firewall from 001 - xxx or the final number body built each day. The next day, the plant would start over with 001 accordingly. It was easier for the assembly operators to see the large number written on the firewall rather than read the small body number embossed on the body trim tag. The sequence numbers helped operators match specific parts to the correct car moving down the assembly line. When the body was complete the body build "broadcast sheet" taped to the firewall (shown in the picture) was transferred and taped to the inside front glass. There is a good picture of this in the Echoes of Norwood book.
I have also seen the body sequence number written on the top surface of the inner heater core box, on top of the fuel tank, and occasionally on the inside surface of the spare tire rim. My 05A '69 Norwood build Z28 had "63" written on the top surface of the heater core box and on the top surface of the fuel tank. There is a discussion on CRG where folks have shared pictures of their original sequence numbers on these components. It appears when the body broadcast sheet was published daily thru the assembly operations, and the subassembly folks must have written the sequence number on parts ahead of when the car showed up at their assembly stations. I stand corrected on this but not sure why this practice has been seen on some parts. What is interesting, the fuel tank was common on all Camaros regardless of engine size and option content. This leads to my speculation that some fuel tank subassembly was completed prior to the body showing up at the assembly station. I assume/speculate that the specific fuel sending unit for an SS or car with a vapor return line which required two fuel lines run front to back vs. Z28 or car that did not include a vapor return line and had a single fuel line installed. Thus, several fuel tanks were preassembled and had a body sequence number written on it to be ready for the corresponding car when it showed up in the assembly station. Off-line preassembly of some components saved time. The spare tire was specific to a Z28 or SS car with 15-inch rims vs. a car that called for a standard 14" spare tire rim.
Attached is a picture of the body-in-white sheet metal assembly process on a 1st Gen Camaro. As I studied the picture and enlarged it, it shows a sequence number 17 in the upper surface of the trans tunnel, on the car the operator is positioning the sheet metal top onto. The next Camaro in line includes what appears to be a 18 written in the same location.
Thanks in advance if folks could share pictures of any original body and component sequence numbers.
Dave
