biggest tire for my Valliant

I have run
Hey all.what's the biggest tire I can put on the back of my 65 Valliant.I have stock ralleys 14 by 6 with a 4 inch bs.
Ted
I think Darts and Valiants will take the same sized wheels and tires. (Measure first) The black wheels on my 66 are 15x7's with a 4.25" backspace. 225/70-15 tires. The Halibrand clones are 15x7's with a 4" backspace (I believe,never measured them) with a 235/70-15 tire. No spring or wheel lip rubbing with either but there is a slight wheel house rub with the 235's occasionally. Not an issue though.

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