A couple pumps for sale on eBay, if anyone needs one.
http://www.ebay.com/itm/Nims-Brass-Water-Pump-for-Ford-Model-T-/190726812628?pt= Vintage_Car_Truck_Parts_Accessories&fits=Model%3AModel+T&hash=item2c683433d4&vxp =mtr
That kind sucks. If water supply is a little low, or it tries to pump more water than is available, it will cavitate, and not pump.
I have experience with those kind of pumps, they are well below the upper water tank, and if it would run out of water, your engine would be locked up, long before that.
"upper water tank..." . . Late radiator, or brass radiator? A pump requires some head (liquid term) or it will cavitate if it is asked to pump faster than its intake can fill. When it cavitates, no water flows. Cavitation in a high pressure pump will quickly erode the impeller and housing.
rdr
Someone wanted them, SOLD! The Nims, made in Stockton CA, if you look at the first illustration, do not have a real aggressive impeller. The one I had was rather flat. The only reason I never put it on my car is because I could not find the correct pulley or I could have done a test. The Model A used a pump in the same place as an aid to the thermal siphon system.
all T Radiator tanks are the same from pump location.
The rest is if this, and if that, and none apply to a T. These neck pumps came out at the time of the early brass cars, and that is where most of what I have seen are.
If you don't have water to feed the pump, that is the least of your worries.