Ok, I was ready to mount the American Racing vintage slotted mags I got on my '75. Lo and behold, there ended up a fitment issue where the calipers were contacting the inner rim. They did fit the bolt pattern correctly and backspacing doesn't seem to be the problem but the top of the calipers scrape the wheels. Turns out the stock calipers are a bit too large to allow the wheels to spin freely much less allow tape wheel weights to be added without stripping them off. Is there a substitute caliper I can install to fix the issue without changing the entire front brake system so I can use these wheels? They would have to be a lower profile and hopefully without breaking the bank.
AFAIK there was only one caliper used on Mav/Comet/Granada. If it's only a small amount, say 1/16", I'd clearance the present caliper.
I had the same problem with my Sprint when I converted to 4 wheel disk, I got some 1/4" spacers and that fixed the problem and did not push the tire out to bad.
My caliper was making contact with the wheel near the mounting surface so I had to push it out just a bit. Where is your caliper making contact with the wheel?