Is G-23 and G-38 mount bolt pattern the same?
Not even close...If the G23 is a new model with the aluminum backplate you could get a G26 (same bolt pattern) and get the same or more performance with less weight...
My tests show the G26 turning more rpm with a Mejzlik 18-6 than a G38 with the same prop....17 1/2 lbs pull on a spring scale...