I don’t think this is what the OP is asking for. He wants Panda to sync to video rate, which should be 120 fps.
Assuming the driver does indeed support 120fps video rate, then Panda can render at that rate, as long as your frame time is no longer than 1/120 s. It certainly ought to be with nothing in the scene.
There’s nothing in Panda that knows anything about 60fps or any other hardcoded rate; if I set my display to 72fps it happily syncs at 72fps. I can’t set my display faster than that, of course, but if I could Panda would sync to it.
If Panda’s still syncing at 60fps, it means that either (a) your frame time is longer that 1/120s, or (b) your driver does not allow applications to sync at faster than 60fps. You can test (a) by examining the frame time in PStats.
Note that you shouldn’t be mucking with the global clock settings in order to guarantee video sync.