Q: Ford Solenoid Switch in Lieu of Mopar Starter Relay?

I have a ford relay on my totally rewired 68 fastback. the car will start in any gear,(bummer)but, the wire to the starter is only hot when you hit the key to start it, not all the time. the box that the ford relay came in said the relay had to be grounded to work. wonder if I insulated the mounting bolts and back of it, if the n.s.switch would act as a ground when starting ??? all comments welcome--------bob
Well, yes, the ground end of the solenoid goes to the case. Seems easier to just use the Mopar part.....