Small Block windage tray ?

I think what the book is referring to is the sides of the MP tray on a 3.31 stroke leave a gap on the sides between the tray and the crank/rods where the oil is supposed to "spin out" and then go out the slots. On the 3.58 stroke, the tray clears the rotating assembly. But there is much less room for the oil to change direction and find it's way out the slots. Also, the longer the stroke, the more potential for windage there is. This could lead to more windage issues. The Milodon tray has a few more slots, and can be adjusted to account for the longer stroke, because it's used on studs, not bolted to the main bolt cap. You could also just space the MP one out a little using longer bolts or studs, and open up the slots slightly, and get the same effect for less $$. The best thing you can do for a longer stroke is a deeper pan.