In an effort to get you exactly the right part we use several resources to accomplish the highest degree of accuracy possible. We utilize Ford Master parts manuals that were printed in 1964, 1967, 1970, 1971, 1974 and 1978. Many people utilize the Ford Master Parts manual 1965 to 1972 "Final printing" edition published in 1975, we do not. Typically original part numbers are deleted in favor of non original service part numbers available in 1975 and much later. The "final printing" Master Parts books continue to provoke debate and confusion over correctness. It will get the job done, if your goal is obtaining driver parts. We also have a huge library of references including Bob Mannel's "Mustang and FORD small block V8", Ford Assembly manuals, Joe Sikora's 1969 428CJ detailing Book, Shelby American purchase orders and part # add and delete sheets, Several original Mustang and Ford car build sheets, MCA judging rules and numerous other quality references. In addition, JD is an MCA certified Judge for 67/8 , 69/70, 71/3, 302 Boss, 351Boss and 429 Boss. We also have indepth experience on the 64 ½ models. We may not know everything, but we can almost always find the right answer. You can email us at jdlarson@srt.com