Without seeing it in person it is very difficult to say. However, I'm leaning toward it beign the real deal stamp. The broach marks are in place and the font size and style appears to be correct. It would be good to see the engine assembly information and casting date.
Was the VIN ever found on the LH rear deck lid seal lip?
MMC/ ICCA Detroit.
The Motor City or where ever there is Mopars
