I think I will actually go with the 300 lb 12 hp engine ole' Wilbur and Orville used. They surely new more than I about the best things to use for airplanes.
Oh, and while we are thinking about it, why should I even be considering putting any electrical devices on my airplane at all? Hand propping has always worked for those old airplanes why not my RV? We don't need radios to fly. And why bother with GPS? Real pilots can circumnavigate the globe using a compass, the stars and a sextant. No alternator, no starter, no wiring, no electronic ignition, no electric trim, no electric flaps, no lights, no need for powered gauges. Lets see now, that should keep things simple. While we are at it why bother with cowling this wonderfully perfect engine that needs nothing other than a rubber hose feeding fuel to it, a mechanical spark producing device of some sort, a carburetor (you can't improve on carburetors so why even mess with that fancy fuel injection stuff?) and some levers to control fuel flow and air flow?
Those old planes were not cowled much so do we really need to put a cowl on this one? Why are we bothering with flush riveting those skins? Planes flew fine before without that "new" technique. Shoot even this wing design isn't necessary is it? Those old flat winged bi-planes flew just fine with them didn't they?
Altimeter, Airspeed, liquid compass and, to keep the FAA happy, an oil pressure gauge for instruments. Just buck some rivets and don't worry about dimpling anything. For God's sake don't be doing anything experimental with those engine installations! Make sure to use those Lycoming or Continentals in these things and quit tinkering with them! Make doggone sure you use the tried and true magneto on there! Oh yeah, I almost forgot! Make doubly sure you are pumping some high octane
AVIATION fuel in it (that is very important too, isn't it? We don't want any bad things to happen because we go and change the chemical composition of our fuel do we? The best fuel in the world is already being used so by god do not mess with that!) That should do it then. Why should anyone ever want to try to improve upon that?