I am no good with small blocks but the numbers you found are the cast numbers. They have nothing to do with part numbers or decoding. On big blocks there is a nice machined flat area next to the oil pan that has numbers stamped into it. This is what you need to find. It may be some place else but it will be an area that is machined flat (think smooth). The numbers that are stamped will at some point have your vin sequence number in it aka "matching numbers". I am not 100% sure of the early stuff to be more help.
