Mine's a '67, but fitment is probably similar. I have 255/60/17s on the back. A buddy has 255/70/15s on a '67 Fury vert. In both cases, you've got to jack it way up by the frame to get the tire in there.
Cragar has some relatively cheap steel 17s available from Summit. I used to have Mustang bullit wheels on my wagon but switched to the steelies a couple months ago.