Ok, here are your options..
The 10x1.25 helicoil will hold the started just fine.. Ask Gest24, he is using one in his 6mt. Just use the tap they give u in the kit and bam, u got a good thread...
Or you can drill out the starter for a bigger hole and tap the existing hole in the bell housing to take an extremeley large bolt... This is what I did on my car and Mikecg's except he got the right bolt for the threads
Tom