I've tracked posts on the subject on several forums... here's the biggest I've heard about:
225/50ZR17 (front) and 235/50zr17 (back) with Torque Thrust two's, 4" backspace on the front, 4 3/4" rear.
On the other hand:
Others reported using 225/65x15's and 215/70/R15's on stock 67 Rallye wheels without rubbing problems.
Several posters reported that 215/70x15's (in one case on a '66 with repro KO's) had caused cracking in the front fender lips after hitting bumps in tight turns (like into a driveway) so they went back to near-stock 205/75x15's.
Recommended for 6" rim:
205/75x 15 or 205/70x15... anything bigger and you need to be really, really careful about rim width and backspace, and hope you don't hit any bumps while in turns, or flare the fenders.
Thanks a lot for the information, right now I have 245x60x15 on the back and 235x60x15 on the front using original bolt on Rallye wheels with no problems. I like the idea of trying the 17 inch wheels with a 45 series tire (gotta get the power down) and torquethrusts look good. I'll report the results after I try them. take care and thanks again.