It doesn't look like an order in the records as it originated at the Adelaide zone office, so it was probably a stock vehicle and Young and Green simply picked it either out of Elizabeth (SA) stock or off the schedule. If it was an ordered car it would almost always appear either through the NSW or Sydney zone offices and would be built at Pagewood. What would happen is your uncle would tell Y&G Toronto he wanted an 1898-18V XX7 van in 4.2 4spd LSD with DL7 (delete) stripes, they would look at the plant stock or at the production schedule to see if there was an unallocated vehicle and say "yes we can get you one in x weeks" if one was there - this is no different to how it works today. The van was completed late may and recorded as sold 6/77 although delivery may have been early 7/77. When your uncle 'ordered' it would be a key piece of information to. Of course it is possible another factor dictated it be built in Elizabeth, but normally you'd see the Sydney or NSW zone office next to the dealer code if that was the case.
Bookmarks