It's possible it could be a fillet-brazed schwinn, which are kind of neat:

http://www.sheldonbrown.com/schwinn-braze.html

One thing about some schwinns is they used a de**** stem size known as .833 inches or... I think 21.5 mm. They're hard to find. I had my sister in virginia buy a sports tourer for me just to send me the stem off of it (I saw it on vacation, I'm in L.A.). You can find them on ebay sometimes, but the only new ones being made are heavy, ugly steel stems meant for chopped cruisers and stuff. I guess you'd have to measure the opening in the headset to see what size it would take.