I thought about a Trek 750 for a long time - I loved the lugs and the level top tube. I never ended up buying one, but I did see that someone on instagram had posted that they fit 700 x 47mm with 5mm clearance in their Trek 750, which looked like a 1991 model based on the lugs and paint job. Of course it all depends on rim width too. I mention this as a data point about tire clearance - that post was a strong point in favor of the 750's tire clearance capabilities.