I have some real '95 R's that was going to go on my '65 fastback. The backspacing on the real R's is 5.95 I believe. Theres really no easy way to make them fit on a 65-66. If you space the front out they wont fit inside the wheelwell. The back actually will fit with a fair amount of clearance. We discovered that if you have about an inch taken out of the middle they will fit perfectly, clears everything and perfect backspacing. Although they do look awesome, it was just to expensive to make them work. Here are some pictures we took while we were mocking them up. Sorry about he quality, it was a polariod that was scanned-no digital at the time.
<img src="http://members.cox.net/stangboy1965/pictures/car/cobrar1.JPG">
<img src="http://members.cox.net/stangboy1965/pictures/car/cobrar2.JPG">
<img src="http://members.cox.net/stangboy1965/pictures/car/cobrar3.JPG">