M-code Dart, Barracuda 69 440 bare block

In my initial add I stated that it originally came out of a 69 GTX. When I bought the block I was told that the 2 threaded bosses were for the factory A-body mounts. With that I had assumed that it would bolt right into a 440 M-code car. If they are for a 383 mount bracket what was the casting# on the M-code blocks?