When I had my rotors done in 1984, the machine shop overbored the one original offending hole to approx 1" diameter. They then machined an interference fit sleeve to be pressed into the hole. They then drilled for the 5-lug studs. As I recall, the offending stud was drilled through the intersection of the rotor and sleeve, which locked the sleeve and stud in place.
I'll have to see if I can get a pic to more clearly illustrate this.
Of course, this was all long before 5-lug rotors were an off the shelf deal. They were the 3rd shop I tried. Couple young former John Deere machinists that had been laid off when the farm economy took a dump. The other shops just really didn't want to mess with it, but these guys were young, hungry and open-minded enough to look at it as a challenge. I often wonder how they made out, you don't find people like that just anywhere, even in those days.
Oh yeah, I should add...those rotors are still on the car today, and have logged over 30,000 miles. Never a problem out of them.