The 6 6 is an assembly date standing for June, most likley, the 16th or 26th. (There appears to be a digit missing from the stamping. Otherwise your engine would have been assembled before the block was cast on 6-11.)

(( or are you saying the car's scheduled production date is 6-11? That would make sense for an engine assembly of 6 6 ))

The HP means it's a high performace engine assembly, compared to a non HP 440, and the 2 means it was assembled on the second shift.

The stamping only signifies an assembly date and nothing else.

the -7 after the 440 is a core revision code meaning the original casting core was revised six times since the original.