I had exactly same question on this forum (with no answer). You can still see my thread on the main page of the tanks heater forum. Supposedly you can change main burner pressure from 5" to 3.5" but you need to connect a manometer to the pressure tap near the main burner tube. I would guess the valve will work even without adjustment but I don't know how efficient it will be in turms of burning the gas at the right rate. I myself ended up purchasing exact same replacement for $80 from online retailer (I am not sure if I am allowed to post the link here, but I can send a PM to you if you want). It turns out that these valves are of very poor quality, they all leak gas from under the gas control dial. Also with the new valve that I replaced the water temperature depends on the ambient air temperature - if it is cold in the garage, the water is hot. If it is warm in the garage, the water temperature drops. I do not know why.
I think White Rogers thermostat may be the better alternative to Robert Shaw / Unitrol.