I've found serveral id tags on my '69 Camaro wire harnesses that appear to be the last four digits of the GM part number. For example, the rear harness tag below is 1692 and the p/n is 8721692 (without the RS option). Likewise the dash to rear harness is labelled 1690 and with the auxiliary lighting option (ZJ9) the p/n is 8721690. The instrument harness also had an orange label 7663 matching p/n 6297663 (with console guages)
Is anyone (Steve) able to confirm that this is correct? There could be a lot of useful information obtained from these.