When I bought my 540, I didn´t buy the 5-stage Verdi pump and tank that the he had used, just the oil pan and the pump mount.
I already had a 3-stage Weaver pump from an old engine.
I did this, only to save some money.
But an open oil pan with only two scavenge sections didn´t work any good, I had more than half the oil in the pan, while running the motor.
Two friends of mine gave me a good advice, to put in slots like louvers.
After that, I had a lot more oil in the tank, instead of the pan.
I would like to try to add one row more.