on the relay, ground is marked with a "G" . the connectors that belong on the relay are keyed , so there is no possibility to mix them up. on my 73 manual car, my ground wire that went to the clutch safety is yellow, so all i did was ground it off the relay to the body. if your interlock or clutch safety happens to be green, then yes, you can just ground it to the body off the relay or just ground the relay and leave the connector unplugged. i dont have a 74 diagram. if you are unsure, you can take a seperate connector and wire, plug it into the G on the relay and just ground it. remember, the car will start in any gear now.