When ordering parts sometimes for my 1979 F-250 sometimes I need to know if the vehicle was manufactured before, or after a certain serial number.
For instance some suspension parts LMC asks if before or after #Y 20,001 .

So in my case I say before, since I have two leafs in each of the springs.
Evidently later in the year they went to more leafs per spring assembly.
BUT, would be nice to find out the actual number.
I don't see it on vin plate, and paper tag on door is not legible.
Any suggestions where to look?

moving right along