The rev hunting is most likely air in the coolant. Bleed it by running the car with the rad cap off and the heater on. No oil pressure is a worry, for engines sitting around for a while I normally turn over by hand first, add a smudge of oil down the plug holes, disconnect the injectors and crank until the oil pressure light goes off. Then connect up the injectors and start it. 4ages run bad with open headers too