I used the entire cowl and did not cut any off. I mounted my Magnum 91 4 stk at a 90 degree angle and ran the muffler out the bottom without any problem. I used a three line fuel system with a dubro filler on the side of the cowl. I almost mounted the engine inverted but choose to go with the stock installation. If you want to mount yours inverted, you can rotate the mount and use the pre drilled holes and blind nuts installed. Good luck!