Can you post a link to a photo of the engine serial number?
Can you post a link to a photo of the ledge/boss on the block, rearward of the distributor, where the Engine Serial Number is normally found?
Can you post a link to a photo of the top of your head (driver's-side rear quarter of the head), with the valve cover off? A date code should be near the valve cover "seat" between the 4th and 5th cylinder valve springs.
A replacement head made in 55-57 might have come without any engine serial number; or, maybe the replacement block might have come with the plant and month codes. The evidence for this suggestion/guess is that some people have shown photos of engine codes with different sizes/types of code letters/numbers.
