[daltondavid]

Well this sure got the keyboards clicking! Mr. Mustang is correct about the installation of some 390 engines due to a shortage of 428 engines. I have never fully investigated when that occurred exactly. I am sure someone out there knows. I would like to know as my car was built on January 5th, 1968 and could possibly fall into that category. I have always been led to believe that all Shelby Mustangs for 1968 started out as "GT mustangs". they were then sent to the conversion plant where they were "Shelbyised", Fiberglass installed, Rims or Hubcaps, Engine installation. Now I am going out on a limb with this one. I believe they were shipped from Ford with 390 engines which were pulled and 428's put in there place. 390 engine then returned to Ford. anyway, That is where the "S" comes from in the VIN. and of course when the 428 CJ engine came along, so did the "R" code. Know if anyone can answer the "when" question concerning the 390 cars that would be helpful.