As the crankshaft rotates while the engine is running, the counterwieghts and throws skim the surface of oil in the pan, and at times pick up oil as they rise. This causes drag on the crankshaft,(imagine moving your hand through water), and slows down the rotation. A windage tray is a baffle which removes the oil from the crankshaft as it rotates. This prevents the oil from clinging to the rotating assembly and removes the drag, increasing the possible acceleration rate and horsepower output.
I had a 74 Motorhome that had a 440 in it. It also had the windage tray and when I ask the dealers about it they said it gave me about 10 hp more due to less drag . It is my understanding, could be wrong here, but I was also told that the Boss 302 also has a tray in them, never seen one apart so can't be sure of that fact..One thing you do have to consider if you instal a tray is to mark the full line on your dipstaick before you instal the tray, as the extra gasket and the tray will make about a one quarte difference on the level of your oil.