Its an 8.3mm drill size...
if it hasnt snapped the rocker shaft you would be very lucky. check for hairline cracks in it. You need a m8 helecoil kit. Dont risk anything else.
I was lucky that my bolts although ripped out were just bouncing about in the stripped hole and not got jammed up inside the head.
Helecoil the lot. its very easy compared to doing exhaust stud thread replacements
http://www.toolsnextday.ltd.uk/Helic...icoil_kits.htm