408, Small or Big Block? Need EGT Info

Rob is correct..EGT readings are pretty much worthless, and completely worthless when the engine isnt under load.
You would need to have the motor on an engine dyno or chassis dyno to get any temp reading that would be of tuning value.
At idle, temps are going to be all over the map off the carb idle circuits. You aren't going to get any data at all worth looking at.
Sometimes... hearing what you seem to not want to hear...isn't a bad thing... your barking up the wrong tree with that EGT probe