What do the numbers refer to?
Passenger side one I believe is an assembler or inspector number considering the numbers we see.
The 8 might be a quick identifier - have not compared (nor know all the axle codes) all the examples I've got pictures of yet
If someone interviewed the retired Ford factory and assembly line workers, and wrote a book about it, I think it would be on the best sellers list (at least in the Mustang hobbyist world). What priceless information to the hobbyist! ;
Not really a big market for the effort and dollars IMHO
And yes, you would hope someone could remember half of these markings and why they were there.
Unfortunately few remember the tasks they did - most only worked a few stations during their time at Ford it seems. The guys that moved around allot and up the food chain are far and few between though I know of some. Unfortunately most only remember who was an a** , who was sleeping with who's wife or who came to work all the time drunk or loaded
Expecting them to remember markings seems to be a real stretch - I've asked
The vast majority of the time they respond with "what markings" or "you've got to be kidding" and you have to word the questions carefully or you'll just get allot of yes's and "sures". just so you'll spend some time with them and keep buying them lunch or coffee
Just my experience but we do run across them on a regular basis locally