I just put a 2F in my 73. I had the radiator cleaned and used new hoses and thermostat (with both gaskets). I am running an older water pump w/o fan clutch. It does not want to get above 130 deg while running. If I pull a long steady climb, the temp guage creeps up to 180, but immediatly starts droping back when I start it. My first thought is the thermostat. Is there something else I should check?