The fact that you had to replace your head brings up the question as to whether or not you had a over heating problem before that caused you to have to redo the top end.

Things that can comonly cause overheating

Slow/ old thermostat- get one from Toyota and check it in a pan of hot water before installing and compare it to your old one. Watch how it opens and closes. A slow thermo stat can cause a motor to overheat especially on a cold morning - the little engine heats up before the thermostat can react , building up excess pressure and often blowing a head gasket.

Also , an inherent glitch in these motors is that when the heater valve is open it seems to cause a regular spike in the temp the engine runs at. When ever I see my temp gauge spike the first thing I do is shut off the heater valve un till the engine levels off at a normal operating temp.

Fan clutch , is yours good? Even a cool running 22r will cycle the fan clutch every so often. If it isn't working it will run hot / overheat.

Radiator in good condition? Water flows thru it top to bottom easily?

Coolant recovery in good condition? If it works correctly, it will purge any air that is trapped in your engine and purge it. Engine heats up , pushes air out , purges thru and out of the recovery tank , and then sucks liquid back in to replace it when it cools. Check the level every morning when the engine is cold. When you first refill your cooling system you'll re-add liquid a couple of times if there was any air left in there. If it continually requires more coolant you have a leak or bad head gasket.

Carbed or F.I. ?

If carbed , make sure your vacuum advance is working properly.