340 running hot

Does it run that temp at idle in traffic, when running down the highway or both? Coolant or straight water?

Did you replace the cap and/or thermostat during the rebuild?

Oddly enough. When I last went through my engine, I had some cooling problems. The new cap and thermostat that I had installed were BOTH bad straight out of the box.
Engine runs hot all the time, even hotter in traffic. If you are driving for any amount of time at around 35 mph it cools down to 180-190. I have replaced the tstat twice and am now running a 165 degree. I tested the cap and it appears OK