Tobin makes an adapter to fit a Corvette C3 caliper which will work for 15" wheels, he makes it for the vintage race guys. Its a little bit pricey, but his stuff is always very nice. Its on my list of upgrades, but I'm still in love with the 14" spinner hub caps on my 65 GTO 23 years later so I'm not ready to make the switch yet. His solution is only for the fronts, but that is probably all you need for what your doing. Lets see some pics of your 66!!