I'M LOOKING FOR A SET OF LONG TUBE HEADERS WITH 3/8" FLANGE TO FIT A 67 F/B GT .. NO POWER STEERING , HAS A 4SPD TOP LOADER ,, AND A 390 WITH 68 CJ HEADS. I'VE GONE THROUGH SUMMIT,  JEGS, FPA, HOOKER ,HEADMAN,  THORLEY, AND NO ONE FOR CERTAIN CAN TELL ME THERE'S WILL FIT  "FOR SURE"   ANY HELP????????????????  I KNOW ABOUT THE USUAL MODIFYING  .. SOMEONE ELSE HAS HAD TO GO THROUGH THIS TOO