Stripped Holes in Cylinder Head for Intake Manifold Bolts
This reminds me, Years back we had a 67 GT 500 here for repairs. The owner bought a 2 four barrel intake and tried putting it on a 428 by himself. After not being able to thread the bolts in due to the block being decked. He hammered every one in flush. He called us after there was an intake leak. Not only did he destroy the threads he cracked the heads.
There are times you need to get someone experienced to help for damage control. Use a 1 inch tall hardened fixture with the proper hole for the drill bit being used. Also make sure the tab from the hela-coil doesn't end up in the engine. Had a Harley here with one caught in the oil pump. Trials can get Costly