Ok, I think this is as far as I am going to go in terms of authenticating this bass. The only other thing I can do is find this T. Chambers fellow and ask him to personally verify it is a 72.
I found this post Help identifying/dating Fender P body
which talks about how T. Chambers stamped other 72 J Basses.
The only other thing I can suggest is to come to Boston and play the bass for yourself. It is set up real nice. I have a pair of Epi's you can play through.