So...I took the car to Status Auto in Menlo Park, CA - they do good business adding bigger wheels and exhausts to Porsches and other german cars - but also have the latest Hunter alignment and wheel balancing equipment and were happy to take a look at my "rad Italian" car.
They took all the weights off first (applied by the tire-fitters a few months back when the tires were first fitted) - the balancing machine and process are great to watch - an excellent step-by-step widescreen user-interface shows exactly what's going on.
2 of the wheels (btw they're 16" Speedline Mistrals) just needed regular balance weights, i.e. the road-force measurement found no anomaly - for balancing the machine rotates and draws a laser line at the midpoint of where the weight should be attached and how many weights - it does that twice, one for inner and one for outer rims. All these weights were being applied in radically different spots to where the tire-fitters had put them - I was hopeful.
But on two it found a road-force problem - the good pair had road-force readings around 6 or 7. These two were around 23-26 and lit up red, with warning messages. Then it tells him to measure rim runout - so an arm folds out and is held against the inside of the outer rim edge while it rotates - after which it draws two more lines (laser) - one on the tire which he marks in grease-pen, then rotates for a 2nd mark on the wheel. Then off to the tire-fitting machine - break both beads, grab the tire, machine rotates the wheel until the lines meet up - then back to the balancer.
One of them then dropped to 5 on the road-force measurement so was cured - then balanced as above with weights.
But one of them stayed around 23. That rim is bent - and it was visibly bent when spinning up for the measurement - not good. But he re-balanced it anyway. We agreed that "at least now I know" and put the wheels back on, the bad one was from the rear-right and we left it there. $140 total and I was there at least 90 minutes. I'll be going back to this place.
Then the 40 mile drive home and...the problem is gone, pretty much. If I get up to about 65 and hold the wheel with fingertips, maybe, just maybe I can feel something, but it's hugely better and really pretty good for at least one slightly bent wheel. The roads are so bad in the Bay Area that I won't notice - 80 feels like 70 used to. I bet it uses less gas too!
I could buy a set of wheels for it, but 1995, 222,000 miles, 80 mile daily drive roundtrip and now I can't feel it? probably not. There are places that can "straighten" bent wheels - but I'm not sure I trust in the process, or what it changes in the metal's properties.
Thanks for all the suggestions above - he felt for tie-rod play before he removed the wheels and he couldn't feel what I mention above - all wheel bearings are good and all bushings in good shape. Time to drive.