Originally Posted by slow rollin

First, start with vintage mountain bikes. since all of them can use that size. Then hybrids. Then touring bikes. Finally, after all that look for 70's or mid range road bikes that aren't targeted towards tri-athletes, racers, professionals, etc.
Or just go 650b.
Easiest way to tell from a look is how wide the current tire is, and how much room it has.
Or looking up old vintage catalogues, seeing that it came with 700 x20mm tires, and realizing that probably won't have tons of room.
Don't forget that not all 28mm tires measure that. Most of my older ones measure 25-26mm and those fit in many of my vintage road racing bikes.
Currently my benotto 1000?(not sure of model) fits a 28, but it had work done to it like spreading the rear end.
Most of my 80's bikes can fit a tire that measures 25mm, much above that and you have to be selective.

Don't forget a suspension seatpost can do a lot as well. I find 23's aren't as bad as people make them out to be, but I run close to "recommended" tire pressure according to the calcs now.