The 521 is most likely too old for this, but the Nissan dealer software now prints out the first sale date, warranty expiration date and several useful fact at the top of all work orders. I would surmise that this software is VIN driven so older non VIN ID numbers would probably not trigger the vehicle production etc. info.
Example: My Infiniti J30T lists the production date, the fact that it was retained by corporate Nissan for a year, the date it was released to the dealer for sale and the date I bought it with the warranty expiration date. Can't ask for a better ownership trace than corporate records.
The corporate NISSAN Zama collection site refers to the original 410 rear end design as "controversial". The change to more acceptable design in the 410 and 411 was made with no rear end specific model change designation. So a P410 can be either old or new rear end and even keyhole or "rectangular" tail light without model designation change. The official Nissan model change chart even completely ignors the 411 model in its generation chart.
Hi, We're a custom shop in Albuquerque. We've been commissioned to do a KA24DE swap in a 71 521 pickup. I saw your motor mounts and am interested in buying a setup from you. I think we have the 240 sx trans as well.