I'm about to find out. I bought a set of '05 17x8 rims for my '65 (it's even tighter than your '67) They added more backspace to '05 and up rims. That's not good. '94-'04 rims are a better fit. Either way you'll need a set of spacers. Try these links:
http://www.mustangmonthly.com/techar...7_inch_wheels/
http://www.mustangmonthly.com/techar.../classics.html
Good Luck