Known overheat issues 4.7 RAM V8? EDIT FIXED

67Dart273 said
My neighbor bought a 4.7 1/2T Dodge plow truck recently, so no real history. It seems to overheat bad on the highway and I did warn him about plow blockage. They tried a new stat. Anybody familiar with "known" issues with this engine? Is there any tricks to filling them? I have not looked at it, he just called me. Heater works REALLY well he says. Bear in mind it's been COLD here high temps last two weeks in low 20's and teens this week.

I told him to try and figure if it is "really" overheating (feel around heads etc) try to find infra-red thermometer.
He said T stat changed things, I even mentioned maybe the new stat is defective
I can't see a rad blockage as it would seem the heater would block first, but ?? (These heaters have tiny passages)
Likely not a water pump or heater would not work "well"

Ideas?

How many miles on this engine? It is a SOHC POS, aluminium head on a cast block. As aluminium and cast iron expand at different rates, the head moves on the head gasket. The number of miles is not exactly the determining factor in when they will fail. Heating and cooling cycles is the control factor. An engine driven on short trips and allowed to get to ambient again, will have many more heating cycles than an engine driven longer distances. The short trip head gaskets will fail at lower mileage than the long trip gaskets for this reason.
To diagnose head gaskets, when the engine is somewhat cool, remove the rad cap. Bend a short U in a piece of welding rod or coat hanger. Slip that under the vent valve so the cap is not holding pressure. Make sure the rad is full and put the cap back on. Now any combustion gas leaking past the head gaskets will bubble in the overflow bottle after the thermostat opens. Quickly snapping the throttle open will bring much more bubbles if the gaskets are failing.
These engines and their V6 relative are a pain in the butt to work on. Most likely require removal of the timing cover to reset the chain tensioners, one for each side.
I did gaskets on a Jeep 3.7L V6, and cussed like a sailor. They had poured stop leak in and plugged the radiator, so it would overheat in a couple of miles. New radiator and it ran like a top. A month later a guy pulled out in front of her, and it was written off.