How handy with tools are you? When I do a re-power I look for engines out of Cub 2160,2164,2165 or a 2185. The first 3 are 16HP Vanguards the 2185 had the Kohler CH18. Your engine should have a 1-1/8" shaft. If you go the re-power route you will need to fab up a new drive shaft, exhaust system, ducting to control the air flow and some wiring changes. This is another option pretty close to a plug and play but you may need to do a few things.
http://www.smallenginewarehouse.com/...tegory=1709178