also check out the Schwinn Forums here; they're not big on those of us Schwinn owners doing SS/FG conversions, but they're the most knowledgeable group when it comes to specifics about your bike. There are a lot of resources to figure out what model/year bike you're riding. For starters, look at the headbadge and see what number is stamped on it (its usually really lightly stamped and can be easy to miss) its a four-digit numebr. First three digits are the day of the year that your bike was assembled (0-365). The last number is the year it was made - the problem is that you already have to know what decade it's from, because it just gives you the single digit. So a six at the end could be 1976 or 1986.
This is also the best resource for finding out more about older Schwinns built through 1979.

I converted a 1977 Schwinn Super Le Tour 12.2 to fixed and am really pleased. Found out everything I needed to know from three sources: Sheldon Brown, this forum, and the Schwinn site.

Good luck.