Here's my '66 Valiant with Coy's 17's sbp. 245/45 r17 rear, 215/45 r17 front. They no the proper back spacing at Coy's for our early a's. Hope this helps!
Here's my Valiant with some later model Mustang rims (they were cheap).
The fronts are a 245/45-17 and would need fender mods at the bottom front to work. A smaller tire or different back spacing might help as well. Just an FYI.