Tire size for a 1974 valiant/dart
I ran 225/60/15's on my Duster on 15x7's with a 4.25" backspace. Obviously the Duster has more room in the back, but the front clearance is identical.
I used the lower front fender corner-to-bumper braces to push the lower front fender corner out to the max the brace would allow. That was all I needed to do for the front's to clear. No issues rubbing after that.
You
might have to trim the flange on the backside of the lower front fender corner back for the tire to clear when turning through to full lock. Not everyone has to, but some do. From the factory the corner of the flange at the lower front fender is square, if you cut it back at a 45* angle you should have all the room you need. It's not visible from the outside of the car really, just if you look at the backside of the fender.
This is what I'm talking about. I did this to clear my 275/35/18's in the front, it wasn't necessary for the 225's on my car at least.