As far as I have seen gravity does not play a role in anything in a PS gearbox, so it's orientation should not matter. I would think that there should be enough pressure and flow from the pump the get the air our regardless of it's orientation.
Just don't mount the PS pump upside down.....I don't think that would work out very well.
As others have said....please do let us know what you are looking to do. If you ignore the people who say don't do anything different ever or we'll all die you might just get a couple good suggestions..... or give someone else an idea or two
Tad
