My 440 is .080 over, no cooling issues at all. Its not the overbore, we have lots of customers cars at .060 engines and no issues. One engine we took apart due to overheating that was "rebuilt" had lots of crud in waterjacket but big issue was old core plugs pushed into the water jacket and left there! Originals are thinner cup shape and one made it up to passage closer to pump, very poor flow resulted.
Some aftermarket pumps have very small impellers, some others are 1/2" away from the curved surface in the housing! Is there a big chunk of crud blocking passages in the radiator?
Deleting the thermostat without some type of restricter nearly always overheats.