Thanks for all your comments.

I finally realized the 130mm spacing is the first and most important limitation, as that's based on the frame itself (after spreading). If I'm doing the old XT hub route, according to the site previously mentioned, 1993 I think was the last year they did 130mm. So there was a good 5-ish year period before that that were 7 speed hyperglide (and uniglide?) compatible, I think at least. So there's that, and you can find some of these on ebay.

So then I started looking at cassettes - there's the sram-730 with 12-32, and even a megarange that goes up to 34 teeth at the top. Oh, and there's lots of xx-28 in seven speeds - all of which, I think, would work. So there still seem to be a decent amount of 7 speed floating around.

But all this got me thinking, will it go with my rear derailleur? Someone switched out a lot of the original stuff, and the rear derailleur is a Super Record campy - the newer variety, rather than the initial SR. People on the forums say it'll only accept up to 28 teeth, and even then it's finicky. The front is the original Sugino cranks, 28-45-50 (but with a NR derailleur).

Anyway, a bit of a mess, and probably beyond the scope of my original question. Everyone was nice enough to respond, so I thought I'd go ahead and fill in the details.

btw The bike came with the original maillard helicomatic hubs now laced to skinny, black, nameless rims. I was originally quite against using the Maillards based on Sheldon Brown's opinion of them. . . . hmm. And I still can't get over that the bike came with a carbon seatpost and a Salsa Stem, among other oddities. Weird.