I'm pretty sure that the Monaro was originally raced by Ian Easton before Jim Richards, but I'll check. I do know that Jac Jac was the first one to put stars on it, and during the election period he ran the "Vote National" slogan because it was fairly easy for farmers to tell the tax man that Monaro's and associated costs were in fact tractors lol.
This photo is from Ian Easton's personal collection.
I think that the car was originally a tarmac race car from brand new but was crashed while driving it from Levin circuit to Auckland at Tokoroa, and then converted to a speedway car.