The Melling M63HV is the "high volume" version of there standard BB replacement oil pump which uses the stock internal pickup and oil pump suction supply passage, stock oil pan. The Milodon system has a special pickup which requires a special external pickup oil pan, and the oil pump cover in the kit bolts to a stock style pump body(either the M63 or M63HV or other pump), the internal pickup is eliminated and stock pump passage is plugged.
I use a Milodon external system and Milodon "road race" pan which has it's own static external pickup on my 512" motor.