The originals are Yankee 77's. I believe they are no longer available new. There are some used ones out there as well as reproductions. The '66 Roof you have will be a little different than the '70 C-60 that you have mentioned.
It would be nice if there was a Factory Template out there, but I have never heard of one and there was none available when I installed mine on my '64 C-30. I went to the junkyard to measure some larger parts trucks there, but they must have been Dealer installed lights and I realized that they were not exactly correct. I just kept repositioning them till I felt I had them factory correct, then bolted them down.
Bill
