If you keep the water pump, keep the thermostat. If you remove the pump, remove the thermostat, and also make sure that you have a head gasket in it intended to be used without a water pump because the water passage holes in the gasket are a bit larger.
I have a B (same engine as an A) that I put a water pump and thermostat on because it got hotter than I liked when it pulled a plow. It is still on after about ten years, no problems. It helps cooling under heavy loads, but causes no problems under light loads.