Anyone know what these ARP 625"s will hold for PSI on a stock headgasket---i guess they can be torque to 150-160 range. I'm thinking of moving up to the BD twins and according to there website that the towing twin require no head modifications. I really don't want to put a 0ring head in until she pops---then just go with the full 9 yards---Orings/ported/valve job/springs/push rods-10 over gasket etc---no need to take the head off until i have to. I think the BD twins are gated to 45-50PSI. Any comments or experiences are appreciated. Thanks DW