Call lakota or midwest on the springs(stick with single unless u have made a billit cam). Some kohlers I have found had lighter valves than others, this is important to use the lightest valvetrain parts that will hold up, and only just enough spring pressure to keep from floating valves at rpm u run. Kohlers valvetrain is nearly 2x the weight of briggs in stock form. When getting into higher rpm 6500+ we have ran into rapid wear on lifter base when using a welded lobe cam even with polished smooth sides, edges and surface of lobe. A fully roller valve train eliminates most wear, I would recommend the lightest adjustable pushrods you can find so u can adjust quickly without swapping fixed pushrods, different height perches, or different thicknes lashcaps when using stock rockers. A welded cam is a weak spot in higher rpm, have seen many break due to heavier valvetrain and spring pressure. I recommend making a billit blank and gear and have the profile u prefer ground. The midwest flywheel is for a twin, there are none off the shelf for a single that I know of. If making your own use a good grade of aluminum and the stronger magnet from midwest. "IF" you can use a handheld starter, ditch the ringgear.