That is very interesting regarding the gauges pictured above. I thought mine were just suffering from fading, but they look just the ones in the second pic ('74-'75).
Specifically, I am trying to source trim and glass pieces and I don't know whether they are interchangeable with other year models. Meanwhile, I noticed some of the wagons have amber side markers and others do not. Some of the wagons have chrome embellishments on the taillights while others do not. Some wagons appear to have insignia on the side while others do not. I cannot find stock/oem photos for the various year models to compare.
A fellow enthusiast friend of mine, "datsunfreak" to some of you, has been a tremendous help to me in mapping out a plan for this car. Despite his wealth of knowledge and professional expertise, I feel badly for asking him so many questions and was just hoping to get info from the collective group. He has already indicated that the 510 chrome bumpers will work in place of the stock black ones on the 610 wagon, as well as a number of the suspension bushings and components.