There is a label with
VIN, perhaps fictional
weight and GVWR or GAWR located on the vertical inside surface of the curbside A-frame not far back from the coupler, but it may have been damaged or painted over. The GxWR will be a large clue to the "rubbering" capacity of the original
axle (In '70s, likely 1,200 lbs).
The
VIN is stamped on top of that frame member just a inches back from the coupler but may be hard to spot under the
paint (I presume they stamp, then paint).
One way I found to see it is in shade or dark, using a flashlight to shine across/along the top surface of the beam to get some contrasting shadows.
You may have to remove some
paint to read the entire number.
There should also be a metal tag on the
axle beam denoting the capacity, plant where built and the serial numbers -- If you obtain those numbers, ID the factory from the Dexter site, call them and ask for the 'Keeper of As-Built
Axle Records' , you can get all the original specs and measurements, bracket options, brake flanges, etc., for the original axle, which will all be of great assistance in replacing the existing axle should that day come, which likely won't be long if the axle is original -- The '70s were a long time ago in axle-years!