I am taking an 80's Schwinn Caliente (a real classic, I know) and converting it into a commuter-ish ride. Just for kicks I put the rims off the wife's chicago Collegiate on the Caliente to see how they look and to my surprise I really like the look of the fatter road tire. Only problem is, I can't figure out what a comparable size would be in a lighter, more modern wheel? And where can I buy such a rim? I don't even know what to call that size of tire/rim. Can someone educate me?
So far I've decided to do a coaster brake wheelset to keep things as simple as possible. If i can find a decent set of rims i may get a cassette hub laced in the future. If that is even feasible. You can probably tell I am not exactly a professional seeing that I am putting fat road tires with a coaster brake onto a cheap 80's taiwan schwinn.

You can yell at me and tell me to search the forums if you want, I know that is a standard response, but I looked and couldn't get a clear answer.

Thanks for your help.