I would certainly look at using a Timecert insert for rocker arm stud threads.

We use these for 911 Porsche magnesium cases for the head studs - they pull out from the
soft magnesium. The timecert inserts work fantastic and don't pull out even on endurance 9000 rpm 2.0 liter Porsche race engines.

I would trust these inserts which are far superior to helicoils.

See the website:
http://www.timesert.com/