or do like ryf and use a Garden Tractor transaxle. They are plentiful and not to expensive and have awesome torque. Some even come in 5 speed with reverse. BMI has one already mounted to an engine for sale in their ebay store. I bought one recently for $25. in a heavy duty 3 speed with reverse. and yes it works with a Horizontal shaft engine if you find the right transaxle. or you can use one with a vertical shaft motor which sometimes can be found cheaper than Horizontal shft motors.