If that's a '78 block, then why does it have round coolant holes, as opposed to the figure eight coolant holes? Is it possible that "8" is actually a "3"? Because that casting number sure looks like "3698830-440" which would make it an early...Pre '76 casting.
So he'd still be misrepresenting it, but it would seem you would be wrong in telling him that it's a '78 block. Interesting.