Order lead time for most cars was 4-6 weeks. There was an internal vetting process for dealer orders prior to confirmation. Orders that were incorrect or specified equipment that was not available were not immediately confirmed. Also, dealer status could delay an order. Beyond that, there were typically far more orders than the plants could build. For the normal '69 model year, Chevrolet cancelled 77,000 confirmed orders.
The date on the tag is when the body production order was released. It is only a general indicator of final assembly; for some reason Fisher occasionally skipped weeks when stamping the tags. The tag was stamped and placed with the order; the order could remain in queue for several days. There is no way a released production order remained in queue for 17 weeks.
The last six digits of the VIN was assigned in sequence when the completed body transferred to Chevrolet final assembly. That establishes the final-assembly date. Bodies were then staged in the body bank. Cars were not built in exact VIN order; they were scheduled to maintain line balance. But, unusual for a body to remain in the bank for any significant time.
The VIN in question was final-assembled 4 months
prior to the 03D body tag. Either the VIN tag or the body tag is not original to the car.
We know all this thanks to the late John Z's excellent article on Camaro assembly process. He was an incredibly valuable source of information and will be missed.
http://www.camaros.org/assemblyprocess.shtml