Reply to "Some good...some bad! It passed the MoT test ... But it over heated on the way home."

The thermostat on the right is the correct Cleveland style to use with the brass plate, and the bypass hole drilled in the water pump.

Some people also like to drill a 1/8" hole into the thermostat itself but I don't really think you need that in the Cleveland cooling design?

I would not worry much about using a 160 thermostat vs a 182. I use a 160. It is fine for this car.

It is almost insignificant in this car. Your water temp will reach 230 to 240 regardless of which thermostat you use.

My idling temps are right around 212 with the 160.

The significant temperature is the oil temp. That is as long as your coolant doesn't boil over. That would be more significant? That shouldn't happen until 252 with 50/50 coolant and a 16 psi cap.

The OIL needs to reach 212 F to boil out the moisture. You will START to cook out other contaminants at 180 but you will not remove the moisture until it boils.

If you don't get hot enough you will cause undue wear and tear, can score the piston bores, over stress other components.

The water thermostat does not control that. Particularly in a Pantera. The quantity of fluid is calculated to arrive at operating temperatures, considering the pressure of the water pump and the distance the fluid needs to travel.