RPM and stock 360 pan
There wouldn't be a ton of rearward G's at 4500RPM and 130MPH for 5 miles. Plus, the 440's had windage trays (stock).
It's not hard (for me) to imagine oil failing to return to the pan as fast as the pump can suck it out.....actually, it's surprising it doesn't happen more. 4 quarts is not a lot of oil.
I read an article way back by Smokey Yunick where he ran a SBC with lots of plastic windows to observe oil behavior. The two points he took away were:
1) Different oils stay apart way more than you'd think. He could add 2 quarts of Quaker State on top of 3 quarts of Pennzoil and he could see it in the running engine as two separate oils.
2) Oil goes all sorts of places besides the bottom of the pan, and likes to stay there. There is a lot of windage and sheer mechanical force acting on the oil. Imagine tossing a liquid into a blender - it flies all over and lots of it stays off the floor.