15 x 7s, what size would you run on a 68 four door dart ?

Roughly 3/4" taller and 3/4" narrower than a 225 60 15. I think they would clear on my car. Front bottom edge of fender being the closest point.
Being a local shop they will likely mount a tire and let you check fitment. A local tire shop did that for me when I got mine.