Originally Posted by harleymsn
Actually, in 1973 the 351W with a C6 was used very rarely. The only such combination that I could find was the 1973 Cougar with the floor shift. Most applications of a C6 with a 351 in 1973 were with the 351C/ 351M/ 351CJ which were all Cleveland's. Perhaps NumberDummy can clear it up.
On the starter side of the engine block there are a series of numers/letters stamped that indicate block size, year of build and may indicate build location. The C6 trans also has identification markings as well. There are a few accurate websites that provide the decoding legend for sorting out what the identification numbers/letters mean. Also, the 351Windsor block has specific height and has distintive intake manifold and head bolt patterns. There is plenty of info available defining the identification characteristics of 351W, 351C, 351M, etc.