My 340 is running hot I think.. I need a sanity check.

Overflow tanks came along somewhere in the early 70s, and at the same time, two-part radiator caps. One piece caps do not let coolant blow as easily, and level is supposed to be one inch down from top, not "full", to provide for expansion.
My 71 and 72 did not come with overflow tanks. Are you using a cap where the center is a separate loose plate?
Does the gas gauge read high also?
If so there may be an issue with the regulator on the instrument cluster.
But anywhere in the " normal" range is considered acceptable.
Use the infrared gun, and just notice where that gauge reads at 180 and mentally note where that is on the gauge.