I just scored a 1964 FEIC Princeton which was modded to 6L6's back in 1985-ish by VA (Fryette, Conrad, or Rivera likely did work) and it is just fantastic. I also have a 64 FEIC Tremolux which is an AB763 with 6L6's rather than the 6V6's. The Bandmaster has some years of AB763 with solid state rectifier, and its a head which is good for lugging (so is Tremolux). The Deluxe non-verb stopped in '64 but I would look at those to, much less dough sometimes and good reverbs are around (even if they do take time to find
I have a Fuchs (local guy here) pedal digital that does a nice plate/spring thing with decay pot too that goes into delay land.
I have later SF Princeton and Princeton Reverbs which arent sublime by any means. I think the cabinet wood being changed to particle board with glued baffle (like a bass cab) is as big of a difference as any other CBS mods in the small amps. My 64 just has a totally different presence than my 78 Princeton. I am not sure if the Deluxe began coming in particle board, but it would likely have been in 72 if so (I would guess yes). The master volume models are easy to spot by the extra pot, but that in and of itself is not a big deal...other mods that came about the same time on bigger amps are generally more ostracized and hard/impossible to undo I think.