35mm tires came stock on the 1993 Streetlife. I'd shoot for anything from 28-38mm.

It's an excellent bike for free.

Pretty decent entry level hybrid.

For mixed use, I'm pretty fond of the WTB All Terrain. Could maybe find it cheaper at Amazon. I got mine as Take-offs at the LBS for $15 apiece.

http://www.treefortbikes.com/product...Comp-700c.html