Use any convenient screw that attaches something to the distributor housing, like one of the spring clips for the distributor cap, for instance. The wire can attach anywhere on the engine, maybe under one of the bolts holding the side cover over the pushrods? Usually, just the metal-to-metal contact between the distriubutor housing and the block makes the connection, but rust or possibly wear on the housing from 60 years of use could give an erratic contact.
Jerry
