I used to have 215's on the front of my car with no rubbing issues. Now I'm running a 195 65 R14.
I just put a pair of 225 70 R14's on the back (today) on 5.5" rallye rims. They look pretty good, but now I'm thinking I should have gone with 235's...
That's pretty impressive! On my former 1970 Australian VG Valiant hardtop (basically a 67-69 Dart and exactly same sheet metal and wheel wells as any 67 up dart or scamp) the best I could do was 245/60 x 15s (BFG TA's) with the rims sitting in close to the springs and they still rubbed the wheel lip a little. I would have said 235/60 x 15s would be the largest to fit on these cars without interference.
I would however say that there is no way 255/60s would fit on the front, with rubbing on the wheel lip a real problem especially when turning at slow speeds and negotiating any little bump in the road .... even 225/60 x 15s would be pushing it in my experience. 215/60s or smaller for mine.
I run 225/60-15's on 15x7 cop car rallies (4.25 BS) on the front of my 71. I lowered it a little with the t bars and have no rubbing issues. I have 245/60-15's on the back with the same rims. After a lot of measuring I figure I could run a 255/60-15 if my rim had another .25" of BS. Maybe someday but the 245's look pretty good back there for now.