73-Engine Fuel & Controls
The choice of power plant options seems fairly straight forward. An IO-320 160 hp Lycoming seems to be the engine of choice for most recent -3 builders. An injected engine would provide the power, aerobatic performance and efficiency that is desired.
In considering a fixed vs a constant speed type propeller, I am not convinced that the added performance of the constant-speed prop is worth the weight, cost or complexity involved in that type of installation. At present, I am leaning toward the simplicity and weight saving advantages of a fixed-pitch prop.