Other casting numbers?
Pecu:
Assuming you know this to be "W" engine, when you say it has no casting numbers or codes, exactly where are you looking? On the "W" block you will find casting numbers on the rear of the block, driver's side. On the passenger side rear you will often find a julian date code (if applicable, mid 1963 on up) or other letters and numbers that represent the build date. There is also a "pad" up front passenger side, just even with the deck of the block -- this has some stamped numbers called "suffix codes". Often these were removed when a block underwent machine work, especially the decking of the block.
You also mention that this is an "engine" and if you have the heads and carbs and intake and exhaust manifolds that came with it you will find additional casting numbers that will give us clues as to what you might have.
Look at some of the other components (pull the valve covers, etc.) and see if you can spot letters and numbers. Let us know if you can find those and we will try to help you figure out what you might have!
Best,
TomK