I bit the bullet and bought two new front tires and bought a third tire for a spare. I talked the tire place into selling me a spare wheel rim for half price and they also mounted the spare tire for free.
The tires are all Kelly KSR1 255/70-22.5 and I had the tire shop install Dynabeads in all three. It rides much
nicer than before, so the ride previously was affected by a really bad balance condition, or maybe the wheel rim's concentricity was slightly off (a not uncommon problem with Dayton-style wheels) or maybe a combination of the two. While it was on the jacks, the technician pointed out that the right front wheel bearing is slightly loose, so I'll have to take a look at that. The left front brake also drags just slightly. That can't be good for fuel economy or brake endurance.
Total price tag for the three tires, wheel rim, beads, three new valve stems, and labor was just under $1200. Ouch. At least this is something I'm not likely to have to replace for a very long time as I'm certainly not going to wear them out by driving too much.
(I've updated the original post with the new cost figures.)