A wiring block pre-forms a cable end having twisted wires for subsequent installation of a plug on the cable end. A back end of the block leading to a cavity within the block receives the cable end such that a cable portion adjacent to the cable end sits inside the cavity. A front end of the block has pass holes leading to troughs extending through the block between the cavity and the front end. The troughs receive the wires at the cable end with the wires protruding from the holes. When the cable end is inserted into the block the wires at the cable end have a length within the troughs corresponding to the plug trough lengths and a configuration within the troughs corresponding to the plug trough configuration with the cable portion adjacent to the cable end having a length within the cavity corresponding to the plug cavity length.