[71 super]

Check back with the manufacturer of the head gaskets, they should be reuseable. Find out the exact process and clean the wee-wee out of the block surface and the gasket before installing. Besure to use the Arp bolt lube as the oil etc will give screwwy torque readings. Check your heads again with flat straight machinist edge to be sure and check ARP to see what they recommend for threads into water jacket. This is aggrevating but should be an easy fix realatively speaking. If the copper cant be reused get the upper end felpro one shot gaskets and you should be good to go. Take your time and it will all be good.