At the Bridgehampton Double 500 on September 20, 1964....several Cobras sprouted the "double exhaust" configuration: 2513, 2290, 2558 and 2557. 2430, Tom Payne's Cobra, ran the same exhaust in 1965....at least during the Mosport Players 200. The reasoning behind the dual side exhaust (just a guess here)...might of had to do with what Shelby American had learned from testing the Daytona Coupe and it's version of the dual exhaust as in relation to high speed tracks (better breathing at higher RPM's?). Unfortunately, I don't have any under hood shots of the headers, but I could guess that the double side exhaust featured 2-1 split headers (Daytona Coupe style) instead of the standard 4-1 headers that were used on most competition Cobras.