Without going overboard on the torque, I'm having a hard time envisioning the studs pulling the threads out. I can break stretch bolts off all day and not hurt the block. I wonder if the block had some previous trauma?
Put those studs on a thread gauge, or maybe Raceware has a length spec.
I suppose the head getting hot enough could exert some pretty hefty pull, but I heated one up till it seized and the bolts seemed fine.
This is the surface it should have
Are the corners burnt off the pistons or precup openings cracking?