flatheads use 2 water pumps stock. One on each bank of cylinders (the V8 was derived from the old flathead 4 cylinder). Obviously there's no room for 2 water pumps in the front, much less one, so he routed it through the freeze plugs on the side of the block. Hell, there may be another water pump on the other side.

Its irrelevant, because that badass looking motor probably makes 300hp. Its basically 8 old lawnmower motors that share a crank. The old saying is flatheads are the most efficient way to create noise and smoke without the annoying side effect of horsepower.