Overheating 360 new engine

This might sound stupid but did you do a pressure test on the cooling system, with a pump to the radiator neck, and then test the cap, should hold at least 14 psi. If there’s a tiny air leak any were it will increase the temp of the coolant with out a pressurized system. I had one that we tested 2 or 3 times, couldn’t figure it out till we tested the cap