As discussed on the HPP forum Dealer 997 is Pontiac motor division engineering and zone 24 is Los Angeles California. Engineering handled cars for auto shows and also provided cars for magazines to evaluate. The Silver Trans Am featured in the March 69 Hot Rod magazine was shipped to 24 997 IIRC.
For accounting purposes I would think GM would "sell the car to itself" as an asset moving through the system.
I think you probably have a very interesting car. It might help others to answer some of your questions if you would post a scan of your billing history sheet.
