That era of Schwinn was freewheel, not cassette. Stick with freewheel, as the options are still plentiful and typically less expensive than similar quality cassettes. From what I remember of my LeTour (same exact color scheme, actually), the rear spacing would not accomodate a late model cassette anyways.

Specs are here:

http://www.trfindley.com/flschwinn_1...0/1987_17.html

Everyone's advice about spacers is spot on. Good luck with your Schwinn...I miss my old LeTour (stolen, sadly).

Check out ebay and CL for quality, affordable wheelsets before buying a cheapo brandless set...as a beginner commuter my buddy went that route and regretted it as soon as he got them home. If you do go the cheapo route (no offense meant, I go that route often) for wheels, bone up on greasing the bearings, properly adjusting the axle nuts, preloading spokes and truing the wheel - cheapo wheelsets are cheap in part because the manufactures do not perform and post-production processing, and usually leave a lot be desired in terms of the amount of grease they use for the bearings.

If you are interested in a quality wheelset that will last you many bikes, check out these:

http://store.velo-orange.com/index.p...te-wheels.html

Retail is pricey, but I picked up a used 700c freewheel set for a great price (ebay) and could not be happier. A big plus, which is hard to find with 126mm spaced 700c sets: factory sealed hubs. Love 'em, and expect them to last long into the future.