Grinding would be required. I have a frame with a brazed-on stop at 7:00, but it still had to be ground from the 7:00 to 9:00 positions. My TdF was tapped and ground long ago, no brazing.
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72 Fuji Finest 72+76 Super Course, 72 Gitane Tour de France, 74 P-10 & 79 Tandem Paramounts, 76 Grand Jubile,84 Raleigh Alyeska, 84 Voyageur SP, 85 Miyata Sport 10 mixte 89 Cannondale ST400 and a queue