Robert Stanton (robron, Bennettsville, SC) took over production of some Rupp karts, he may be able to help you with upholstery and the pedal, 843-479-6962. I know he has the competition wire pedals (A-bone, Chaparral) those mount on the front bumper that would give you another 3 inches of legroom. There is an Ebay seller (gatesflyingcircus) that has A-bone upholstery in black, contact them they may be able to make it in white. The D300 is basically an A-bone with the cast pedals, a welded on engine mount, your kart could be converted into an A-bone with the wire pedals, cut off the engine mount put a swing mount on it and a seat back fuel tank you would have an A-bone.