i recently purchased a book on rebuilding small block fords and in the begining chapters it goes over casting codes and a reference table decoding the numbers and letters for the block itself. i went to look at mine and came up with third position as the "car line" and it says its from the thunderbird line. does this mean the block is out of a t-bird? there is no evidence of the motor being removed from car and all the other castings match up as the mustang line. let me know what you guys think.