megablock and crank

What did I just buy ? Casting # 2468330-m date code 7C20 . Has M C in triangle ,440 siamesed block . Brand new how many years ago ? Also got a new 4.5 stroke Crower forged with BBC rod size but 6 bolt flange same age . Is it one of the junk castings or did I just get lucky ?

Here´s one old topic, if you do a search, there are more.
https://board.moparts.org/ubbthreads/show...rt=all&vc=1

Tom