Engine build date codes??

There all 68 and up 225 slant six's. One is a from a 72 scamp, one from a 73 Scamp. But the one that is marked 2333 has been rebuilt, with a newer stlye head (not the tube type for the plugs 78 and up) and some other mod's. I picked up the motor without a car and just was wondering what year the block was? There must be someone who knows. Thanks