A Little Help Please

A logical explanation to this, When Ma Mopar cast blocks they were done way in advance. I had a 6-6-71 340 block that was a cast crank motor and the year on the pan rail was showing it as a 3Bxxxxxx. The actual build date of the engine in fact backed this up on the drivers side front of the block. The larger thrust bearing was a 1974 release, but the block date code would be much earlier.