didnt look like there was much info but ill look some more. According to the rules for super modified it says " Engine must be originally manufactured for use in lawn mowing equipment and be stock in appearance, with the exception of air filter, air cleaner or velocity stack. Crankshaft must be in original orientation and clearance hole in the frame. Engine may be internallyTHERE IS A LOT HERE YOU JUST HAVE TO ASK THE RIGHT QUESTIONS. SOMETIMES I JUST START AT THE BEGINNING OF THE FLATHEAD SECTION AND LOOK! YOU WILL BE SURPRISED ON WHAT YOU FIND!