Windage Tray

That the it increasing horsepower by decreasing drag would seem to be a misnomer. My longtime machinist, L. D. Smythe (a former SS/A and SS/B Superstock racer) has told me that in development, Chrysler found that windage trays helped only minimally when the clearance between the rotating assembly and oil in the sump was minimal. He went on to say that my Milodon deep pan w/o a windage tray but with an oil scraper would be the best setup for a wet sump.
So, for a bone-stock setup, it won't hurt to use it, and it may help a little. I just don't think I'd bother to install it if it was the only reason to pull the engine. If you are going to install it, you also might consider installing accel/decel baffles in the pan as well. It's not hard to do and will prevent engine-damaging oil starvation.

Bryan