I took the outer half off of the stock muffler and braized the seams and holes closed. Then I cut a hole in the bottom and braized on a piece of 3/4" pipe for the outlet. I ended up with a narrower muffler.

A 20x10 or 22x8 works well on that engine, depending on the type of plane.

You can mount the engine turned any way you want. The carb pumps and meters it's fuel in any position.

Jim