Thanks for the responses everyone. I am not sure I am reading Sheldon's website right, but I think I might be able to get an old 126mm 7 or 8 speed Dura Ace Uniglide hub, and
replace the Freehub body with an 8-speed Hyperglide unit FW7403. Then, with an 8-speed Hyperglide freehub body on it, I would be able to use any 8-, 9- or 10-speed cassette that doesn't include an 11 tooth sproket.
Of course, this would take some doing, and I don't have the special tool needed for swapping out the freehubs. But I think it might be theoretically possible. The entire rear triangle is aluminum, so I might be able to spread the frame by hand to take a 130mm hub, but I would more nervous doing it on this frame, just because of the age and the materials.