Lynn,
I agree with you concerning the extra HP. The old saying "the only time you have too much power is when you hit the start switch and the plane flips over" is one I subscribe to. However I have come to the conclusion that the O-320 is going to force me to fly above recommended gross weight. Today I read the Varieze flight manual written by Rutan that came with my airframe and ol' Burt will allow 1100 lbs GW under certain circumstances but that's it. I have an engineering background and tend to err on the side of the designer, especially Burt. With the O-320 I will likely empty around 725-750 lbs, granted that it's a guess right now but close I think. So 1100-750=350 lbs, I weigh 230 so now were down to 120 lbs left. I can get 25 gals in the plane so now I'm over by 30 lbs and I don't even have a passenger to enjoy the flight with. I can live with a lower cruise speed. If I go with the 190 CI Corvair, which produces about 125 hp I can have my cake and eat it too. The Corvair actually weighs less installed than the O-200. Check flycorvair.com for data. I have several hundred hours of corvair time and can attest to their power, smoothness and reliability. No reason it should not work in this application. Now all that said, I am not saying that I will use the Corvair but it is a strong contender in this decision. They are much lower cost to build and overhaul as well.
hoping for comments on the idea