You'll need to make sure to match the governor drive ratio and direction to that of the engine, for the front crankcase mount it is probably 0.895:1 and CW; effectively similar to a certified IO-390-()()B6. The rear mount location on the accessory case is typically 0.866:1 and CW; effectively similar to the certified IO-390-()()A()6. Not sure what configuration you have here, EXP340 is a Lycoming internal definition.
Not sure exactly what you mean by underthrow mount, do you mean you want the cable coming up from below with the cable basically vertical?