I need a carb for an 84 F-250 with the 300 motor.. It runs extremely rich, fouls plugs very quick, floods easily, lots of black smoke. Pulled it apart cleaned the hell out of it and no improvement, and I can turn the screw all the way in and it keeps running.. I cant get re build kits or replacement carbs anywhere around me. Any cource online for a cheap OE replacement carb for the I6?