318 X block

I bought my Duster used, the previous owner had put a 318 in it. I was out taking things apart for a magnum head swap and noticed it's the "race block" with the big ol X cast on the front.

Should this mean anything to me other than its probably a pretty good block? I don't know much about fancy things like race blocks.
The "X" up front means it is a race block. Search for other numbers!
These block are super strong!