You'll have to:
1) Find out what threads those are in the frame. Try using a known bolt.
2) Check the diameter of the stock bolt
3) Hope that adding a helicoil or time-sert will reduce that hole to the diameter you need regardless of threads.
a) If the threads are the same or can be adapted (by using a time-sert) your GTG.
b) If the threads can't be changed (by using a Heli-coil), get a bolt the right thread for the heli-coil and the right diameter for the mount and use a thick fender washer under the head of the bolt. It will be a fine permanent fix.