My radiator is in the shop right now 235/55-57...4 lbs. cap with rubber gasket and overflow tank. Keep anti-freeze level at 3/4" above the top of the radiator tubes.....these are low pressure radiators 4-7 pounds 180 thermostat and use at least 50/50 mix...NO a higher pressure cap is not recommended as per the radiator shop. the PO had a 17 lbs cap on it and it split the top seam on the tank...just thought I'd tell you what I learned today. T/C Steve