AC model D (I think) road grader

My neighbor has what I think is an early 50's AC model D road grader with what I think looks like a WD45 type gas engine. Two
questions here; Until last week I never used it before. First thing I do is always check fluids and I noticed the radiator and
engine was half empty of antifreeze. I know that the guy who usually uses it was fighting with some kind of "running hot"
issue because he put a home made coolant catch tank off the radiator fitting at the cap. Started thinking about it and noticed
that the water pump had a threaded plug at the top and a small hose (also plugged) coming off the (rather remote in my
opinion) thermostat housing. All I could figure is the water pump must stay air locked and the thermostat also must not be
able to get circulated water enough to tell it when to open. I put a hose fitting in place of the water pump plug and ran a
heater hose to the thermostat housing with a restrictor (a 3/32" bleed hole) in between figuring the air would be allowed out
of the pump and the thermostat would now get circulation. Started it and it ran and graded great without a trace of getting
hot or spewing fluid. So my first question is; Is this the way it is supposed to be because I've seen others with the water
pump fitting plugged off?
Question two; The manual steering box in it is all but completely shot. I was thinking about adapting an automotive power
steering box and wondering if I could simply power it by using (splicing into) the return line from the blade height control
valve body? Anybody done such a thing?

Starting in the early 50, about the time the "45" came out there was a bypass as you describe from the thermostat housing to the water pump. I don't know if there was a restriction in it. The ED-40 I am working on now has such a bypass and in the thermostat housing,even though the hose connecting it to the water pump is about 7/8", the hole that coolant actually flows through is only about 3/8". I think recycling some of the water without going through the radiator would moderate the shot of cold water when the thermostat opens, and maybe when the thermostat is full open not enough coolant bypasses to matter. I don't know exactly how it is supposed to work though.

This is what I was thinking because it looked like a "cobbed" job (nothing any factory would do).

The intention ofengin the bypass was to warm up the engine faster. With the bypass the engine gets warm water earlier before the the thermostat opens. They say engine wear is greatest when the engine is cold and the oil flows slowly.

I have a power steering box setup off a gas d grader its yours if you want it. im in PA

Picture? price? contact info?