overheating and the coolant system

I have a 1959 Fordson Dexta 3 cyl. diesel. I tried plowing with it in the wrong gear (3rd low) but it overheated and steam started coming from the radiator. I let it cool off and drove into the barn. It did not overheat when I just drove it around. I drained the coolant and flushed a tiny bit with some water and then filled it with coolant/water. I have checked the thermostat and found out that someone had already removed it! The radiator fins are fine and clean. I have filled it completely up with coolant and there is no air in the system. The temperature gauge is broken. I then took it out and tried plowing with it again to test it under load. This time it did not overheat at all. Some coolant came out of the overflow hole under the fill cap, but I have heard that is normal if you have filled it all the way up. The radiator hoses and the water pump got a little warm and you could tell that it was slowly warming up, but nowhere near overheating and it handled plowing fine. Can I assume the water pump is OK? Remember there is no thermostat. Should I install a thermostat and how important is it? How do I install a temperature gauge? It looks like I need to raise the fuel tank. How do I do that nd is there another way? What is the result of driving it without a thermostat? All advice and help is appreciated. It is very important to me to restore the tractor and have it working correctly. I also rely on it for my hobby agricultural production with plowing, harrowing, etc.

Without a doubt put a thermostat in it. The engine needs heat to run efficiently. Oil needs to get hot to evap. moisture from block. If not, sludge will form. I run a 180* stat.

Hello jasonteem,

Put in the thermostat that belongs in there! The engine will come up to operating temperature much quicker,
and run cooler as well. Make sure the radiator cap is working, and it is the right one for the engine.
Pressure is needed to have good coolant circulation,

Guido.j