[Heybuck]

I think you should be using the HIGHEST temp thermostat you can.

The stock radiator should be fine. A huge radiator is not always the answer.

If the thermostat cracks open too early (at 160), the engine is pumping the coolant through the radiator FASTER than the radiator can dump the heat into the atmosphere.

So, the coolant is still too hot when it enters the engine again.

A high temp thermostat SLOWS the coolant rate to the point where the coolant has dumped its heat out through the radiator BEFORE it gets called back into the engine.

PS, make sure you have a spring in the top and bottom radiator hose.

Experiance is that marvellous thing that makes you recognise a mistake when you make it again.