Hi Steve 1975,
first of all, Great looking van! Secondly I can help with one of your questions. The body serial number stamped on your firewall is specific to Sydney built cars and this number is different to what is on the ID plates. I had lots of questions regarding my HJ sandman Kingswood based ute and I had my questions answered and confirmed the authenticity from Holden Historical services. email Ben on team@holdenhistoricalservices.com.au with all your ID plate details and the firewall body number, engine number and they will confirm the vehicle on the holden register. This will add value to the prospective new buyer knowing its genuine.

regards
Fred