as usual sydney/bore-troll doesn't know what he is talking about. What you need is a Nitto Technomic stem. Comes 22.2mm quill dia. and is very tall. They also come in many different reaches. You simply take a bit of sandpaper working to progressively finer grit media to bring the quill diameter down just a bit to fit into your SS steerer which has an I.D. of just under 22mm. Its a better alternative than honing the fork I.D. which some do. Go to Sheldon Brown's/Harris Cyclery's site and they talk about them. You can find them from time to time on e-bay as well. I have one on an early 70's Paramount and they are very nice.
Here's one with 4 hours left:
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW
If you get one, be sure the stem clamp dia. matches your handlebar dia. Your super sport has a 1 inch bar...so if you purchase the 26.0mm stem, you will need the Nitto shim which they also sell.
Enjoy that old SS.
George