Biggest tire and 15" wheel possible on a 1966 Dart?

Had any problems with tires rubbing in bumps with those 255 ? Hm, yeah I guess, it seems that there's plenty of room going in but much less on the outside though that's what I expected, it would be interesting to know if anyone has squeezed in anything even bigger without mods, Offset on the rim is no problem, have a workshop-owning friend and we have changed offset on many a wheel!