If you take 427 cubic inches, you will need a little over seven quarts to fill that volume. If you roughly say the area below the piston is clearly greater than the area above the piston, then you'll easily have the room for the seven quarts without ever getting up to the heads at all even with half the pistons being down at any one time. Driven gently, you might not ever even know you've over-filled it that much... maybe.
