You have an old V8 ford motor how can you find out what year and size it is?

You'll have to look at the casting numbers. I'm not sure if its the same on big block but at least on the small blocks it is located on the block above the starter, which is attached to the transmission and is at the rear right side of the engine block. If you can find it, post it on my messageboard and I can decode it for you to tell you the year and size.