There's no comparison with Joss shaft tapers then, and now. Then, if you're talking late 60s and 70s, shafts were quite large by today's standards, 13 1/4, 13 1/2, and even larger were the norm. Also, pro taper meant just that, the thickness stayed the same for at least the first ten inches or so, then gradually widened. Today, the standard, including Joss would generally be thinner at the start, and gradually increasing, rather than a constant diameter for that section of the shaft.
A whole host of reasons for the difference. First, slower napped cloth was the standard, mostly Brunsco wool, as well as Mali cloth. You had to slug the cue ball a lot harder than today. Second, pool was mostly played by men, with larger hands. Also, the cue butts were much thicker than today, so the shafts naturally were thicker as well. Today, with faster cloth, the shaft thickness has gone down to more like 12 3/4 and 12 1/2, with gradually increasing diameter all the way, not the constant thickness they used to be for a large part of the shaft. Most of today's cues, including shaft tapers, do not resemble the ones of that era.
All the best,
WW
It would be interesting to take a dozen cues to try out on vintage equipment like the tables/cloth you mentioned, and use the same type balls from that era.