67 Fury with a 383 - anyone know what pipe thread size is on the engine block for the heater hose inlet and outlet? Wanting to convert it from 5/8" to 1/2", very annoyingly, the heater core I've got is 1/2" on both barbs, and I bought a whole length of 1/2" heater hose and of course I neglected to see what size the outlets were when fixing up the heating system.