Is it the engine that is running to hot or is it the cooling system not operating properly?
An overbored block will run hotter. If the walls are to thin it may run to hot to correct.
A 160 thermostat is in order. If that isn't enough then a thicker core radiator may be needed.
Installing the headgaskets backwards will also create steam pockets and make it run hot.
Hopefully it is something simple and easy to correct.
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