torqueing mains and treads came out. now what?

Helicoil will work just fine and be stronger than the original threads were. However, the hole will need to be drilled perpendicular to the block so I'd have a machine shop set it up in a Bridgeport or something similar to have it drilled. If it's a little off it will either move the main cap or change the clamping load so I'd want to be sure with that.