I get most of my data from the state business licensing websites. If you search "Chevrolet" in OK, you get
this list. If you click on the record ID, it will tell you when the license was granted. It is a LOT of data. Unfortunately, you can't get a query that shows the dates on the main page (results of the prior link) so you have to click on every one individually. It doesn't provide zone/dealer# either. I put it all in a spreadsheet and sorted by date licensed/alphabetically to make assumptions on what "could" be the dealer number based on known ones from NCRS and the chevelle site. You can create your own search (like Seltzer)
here. I suppose if one wanted to pay the nominal fee, you could retrieve a more comprehensive list from the state. Hope that helps!