Just an update, in case anyone's curious. I've looked at just about every Stella-related piece of information on the internet, and I still can't figure out what bike I've got. I think I can rule out the SX-6, though; none of the pictures I've seen of them match up to the bike I have (I have more intricate, long-point lugs with integrated pump mounts, more paint detailing, a partially-chromed fork, fewer eyelets on the rear dropouts, etc.)

Also, it seems that I've got some non-original components on my bike. From all that I can gather, I should have Campagnolo Gran Turismo front and rear dérailleurs. I think the bike might have had Campagnolo skewers as well (is that a reasonable guess? Campagnolo skewers with Normandy hubs?). At least one of my sew-up rims isn't original, but I think the Normandy hubs are (I have matching hubs, but the front is laced to a Mavic Championnat du Monde, the rear is laced to a Fiamme). Someone took the stock hubs and had a sew-up wheelset built using mismatched rims?

Looking at the frame only, my bike looks identical to all the SX-73s I've seen, with respect to lugs and geometry; my paint doesn't match the paint of the one SX-73 I've seen, though, and nor do my dropouts.

Still a mystery. If anyone knows how I might go about searching for old Stella catalogs, please let me know...