Check your timing. If it is retarded the engine will run higher than normal very quickly. You will also see your exhaust close to the headers begin to "glow" with a retarded ignition.
Check for vacuum leaks as well. This would cause a lean condition leading to high temps.
Since you are breaking in the cam; disconnect the vacuum advance and plug it. Start the engine and bring it up to around 2500 RPM and set the "Total mechanical Timing" around 34-36 degrees. Continue with the cam break in run. Watch the water temp, oil pressure and check for leaks. Don't worry about adjusting the carb until after you have completed the cam break in.
Another thing to look for is enough air flow thru the radiator. Are you running a clutch type fan? If you are, it will not be sufficient to pull enough air thru the radiator with the engine stationary. Place a 'box fan' in front of the radiator for additional air flow.
Replace the thermostat with a 180 degree one.
Be sure to replace the oil and oil filter after the cam break in period.