So everything was great, that is to say not overheating. Did this engine ever run and not overheat?

Then you changed a couple things and now things are bad. The radiator might be a problem but they are a very simple concept. So my guess is something ain't right with that water pump or the thermostat isn't opening.

Is the pump working? That is to say... pumping fluid. Is the thermostat opening?

I'm wondering why you messed with the timing at all? As mentioned 6 deg is way off.