I finally figured out that I have a 351c in my car but the vin shows the S code which to my knowledge means it should have the 390 4-V 335hp engine in it. Does anyone know where I can get 390 that is a correct application for my car.
The length of the search will depend on just how correct you want to be. Several of links on this site will lead you to people who can source a rebuildable 390 GT. PAW sells 390's ready for assembly, but one of theirs may be from a range of years. Make sure to get a 390 with the right heads as the bolt pattern is different for 390s in Mustangs and Cougars. I don't know if headers will fit regular 390 heads, but both FPA and Hooker makes ones for the Mustang/Cougar specific heads. If you go with std exhaust manifolds you will need the exhaust manifolds made for this application. I will suggest you post the question at www.fomoco.com/feforum/