I agree, the sears engine is probably a 22cc. I'm not necessarily planning to fly it, but I've been using it as a test bed to see how to perform a conversion in general. My goal is to develop the skills required to convert them without purchasing ready made parts. So far, I have machined the flywheel, created a prop hub, a rudimentary engine mount, and mounted a prop to it. I'm going to bolt it to a test stand tonight and fire it up. Here is a pic of the progress so far: