I agree with Jeff, maybe we should break this thread off the J code one to avoid confusion.
Rich, I think you are confused about my statement. About 98% of what I see are Shelbys so that is my data base however I do not think (99.9999999%) that there is any difference between the CJ put in a Mustang or a Shelby and therefore the engine codess are exactly the same. As far as this 68/69 thing, 407 J is only for 68 automatics and not for 69s so if it is 407 J it is a 68. IIRC the 69 auto code is 421?