I would agree with the post that says they are all good, but there are differences depending on the year. I'm a novice but am studying hard. When doing maintenance or trying to keep a bike factory correct, one just needs to be aware. 1972 for example, has electrical differences as well as seat- handle bars-- switches,etc from both later and earlier models.Fork seals from 1973 and 1974 are the same part, but different to change out on the 1972. For me it is much easier, for example, to replace fork seals on my 1974 than on my 1972. I suppose this comment doesn't amount to all that much, but could save a little time and money when it's time to work on whatever you buy.
This forum is outstanding for advice-- ask as much as you can-- these guys are tough to stump.
Good hunting!!!