I'm no aerodynamic engineer but,

It's a great idea to use a reduction drive, to maintain the engine at it's design RPM range and to give it more torque to swing a larger and "heavier", aerodynamically speaking, propeller. With a higher pitch , at least in theory, it's possible to reach high speeds, but not 200Mph with a 37" pitch at 2000RPM, that would require at least 5000RPM. you can increase further the pitch, but that would make things worse for the low speed performance. The prop which you said, would be stalled for sure at 25 degrees (which is it's angle of attack at .75 radius, given by the formula Atan(Pitch / (2 * pi * ([email protected]))) in static conditions, so the thrust developed by it in this consdition would be very small, thus reducing a lot the takeoff acceleration and increasing the distance required for it.

For high speed flight, it's better to have a high pitch prop, revving at high RPMs, but there will be a compromise in the takeoff acceleration. Take a look at a Ducted Fan unit and see how high is the pitch on the fan blades, and they swing at 20000 plus RPM. The low speed blade stall is reduced by some amount by ducting the air flow, but airplanes equiped with them still require a long takeoff run.

But, it would be an interesting experiment, although the plane, even if perfectly clean aerodynamically, wouldn't exceed 90MPH with the prop you mentined at that RPM.