I don't know how HP can be picked up in an oil pan, but going dry sump there's definately some good gains. There's definately some gains by cutting down on the oil pressure and running thinner oils. i know people running 0-30 oil and gained as much as .005, but that's with a S/blk. By the way my friend with the old 49 ford truck not chopped with stock frame and ladder bars, got some new tires and ran 5.39 friday no additives. That's a 572 rat on gas and over 3,000 lbs with all glass and roll up windows.
Zip.