I’ve got an H16 that I rebuilt the tractor but not the engine about 9 years ago. It served me well until a couple of years ago and the engine just locked up. I haven’t looked at it yet just parked it. I’ve read about many repowered with the twin vanguards and Kohlers. I haven’t put the decals on it yet maybe I should wait and see what engine I use like you mentioned your H18 lol.