I'm going to look at a 69 fastback this evening that the owner claims has a 351C in it. Not sure if it's a 2bbl or 4bbl. It is an automatic. My understanding is that the 351C wasn't introduced until 1970, so if it's really a C then it was swapped in at some point. Question: How can I dfferentiate the 351C from a 351W? Any casting numbers that can be seen with the engine in the car? Thanks.