Just found this from a post about the 340 low pro Milodon pan...

"From what I remember Milodon explaining to me...

The low pro has a false wall at the back of the sump. And a lip. That why there is a cutout on top of the steering linkage. The idea of the false wall is to maintain the same rear sump wall height at the 1" lower pan. The height of the rear wall of the sump keeps oil from spilling into the rear of the pan

You can do this in a small block because the rear part of the pan is only low to clear the oil pump. It's not that low to clear the crank.

The kickout on the bottom sides isn't just for capacity. The slope keeps oil whipping in the sump from climbing up the sides of the sump and returns in into the sump before it hit the crank."