I have a question for those of you with experience of more than one vintage FG, which model do you think sounds best?
That's a loaded question!! Typically, it's the one you have. But, to me the older, lighter Red labels sound a little better than the later models. They started building them a little heavier with the White labels, and the 80's models are even heavier with heavier finishes. BUT!! Even within the same model you can find a dud or an exceptional guitar.
I've done neck resets on (4) FG-140's and they all were excellent. The FG-180's I've worked were a bit more inconsistent, some being a little boomy in the bass. But it depends on what your style is and the sound you're looking for. I like fingerpicking, so a light & responsive guitar is preferred. The FG-110 is was my favorite for a few years. I find the FG-75 to be boxy/bluesy sounding, but it was changed to ladder braced with the Black label FG-75-1 and sounds much better. I've had (2) Black label FG-110-1's and played a couple of FG-180-1's and wasn't impressed, they weren't quite as good as the original version, but they weren't bad, just not as "alive" as the earlier version. But, maybe they were duds, you never know. You have to try various models and judge them with your ears.
And of course, check for high action and a bad neck angle, that is very common with vintage acoustic guitars.