550,

You'll be farther ahead if you just get a .40 sized mount for the engine you've got. It's the right size for the plane, and will use a lot less fuel. The mount may require new holes, but that's still easier than making the new parts, and getting another engine from your neighbor.
Get a Great Planes adjustable mount at the hobby shop, and put on the .40 you've got-it's a good engine by the way.
DB is right about the Hitec radio, I own two of them, and they are a good value and have a few good feature on them, and I got mine from Tower on sale for 109.99!