I have chatted with many Fender enthusiast and have been told the era does not always matter for quality. Yes, the 70's Fenders tend to be heavier but I have been told by many long time Fender collectors that there are just as many pre CBS dogs out there too, but the label of pre CBS makes them more desirable (and expensive) but not better.
I have a '75 Jazz bass that I believe will match any era Jazz bass; weighs 8.5 lbs, the body is swamp ash with slight flaming and is almost one piece (the second piece is only 3/4 by the controls). The neck is to die for and it roars like thunder. I got lucky to say the least. As I mentioned before, my '74 P is a great bass too, normal weight, good quality. The moral of my little story is, if it's a player & it speaks to you, bring it home! Don't worry about the year, the finish or knobs... If not, keep searching.