Well now it was out, a small task of removing broken bolts.
Yep, tried the weld a nut on method. Failed.
Tried the drill small and managed to snap a 1/4" drill in the middle of one bolt then two either side of the two big holes.
Drilled around the edges on one broken drill and then with a diamond point chisel chipped away for just on 6 hours. I managed to get all of the old metal out and no damage to the threads in either hole.
After getting out the dirt and crap I ran a half cut bolt and cleaned up the threads. Now on to clean the case all up and put in new seals.
Cheers,
Ian