i'll try my best to help as you have actually taken the time to post what you have done ...
is the radiator core blocked with dirt and debri ??Take it out and give it a steam clean
Is the temp sensor reading ok when driving on the flat .Thoug they aren't problem as such
I'm guessing you have an XE engine with the twin cylinder heads ?? If so they did crack at the rear of the block ,but was never known to cause overheating.If removing the heads get them pressure tested ,you will need the new multi layered gasket set and you will need new cylinder head bolts.You will also need taps to clean the threads in the block,or else you will get a false torque...do you have the electronic viscous fan ,or the normal one ??is it locking up when engine is overheating ??
norb, September 2013