Nathan,

I'd definitely keep the retracts and the plane will just fly better and look better when the gear goes up. With the power available from today's engines, the small weight added will be much less than if you try to retrofit fixed gear. As far as what engine.. I suggest you look in a Tower catalog. Usually, they have all the mounting dimensions. That will probably give you an idea of where to start. Even though the plane does have a beam mounting system, you can always fill the holes with epoxy/cabosil and redrill to whatever engine you choose. Today, the manufacturers are putting bigger displacements in smaller packages.. so just see what will fit. Post a picture of your rebuild.. I'm sure others would like to see it. Good luck with your project, fly something unique instead of one just like everyone else has...

Dan
Carolina Custom Aircraft