41 - 413
S - 1962

That's the correct casting number though it's not unique to the MW engine and my info says the block was only notched on the exhaust side.

As for the HP stamp (low compression version), it's either got that or the HPHC (high compression version) stamp as well. With the fonts being different, looks like it could be one.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.