I had the engine rebuilt and re installed it

now the gauge in the dash reads 260 deg but a thermal gun is 220 or so.
replaced rear temp sensor. still pegs out.

thermal gun shows about 20deg hotter at the back sensor to front sensor.

thermostat is opening

does not overheat to the point of opening radiator cap

put on a high flow water pump. radiator is newer and was flushed before reisntalling.

electric fan does not kick on.
wired it direct and temp still went to 260

any ideas??

is it possible the head gasket was put on wrong? why would the back of the engine where the temp gauge sensor is located be so much hotter than the front?