While the 3 blade props are generally more aesthetically pleasing, a coarser
pitched 2 bladed prop will always be more efficient (i.e. faster for the same
HP).

I had other concerns which provoked me to go 3 blade. With a max prop diam. of
73 inches (ground clearance) I felt a 2 blade prop of that diameter would not
effectively handle all the horsepower.

Do you think operating that carefully built ("customized", perhaps?) IO-360
without
an air filter is really a wise choice? I'd be concerned about dust and
debris
damaging the engine.

It's not my preference, no room to put in a filter and still have room for the
ram also. I intend to change oil very frequently. and I do have a S.S. screen
in the intake to stop large stuff (more than 1/16th inch). I also plan to be
very careful about dust conditions etc.