Well, you mentioned the Hydro-boost; I had a Chevy dually that had one on it, and I think it is a wonderful alternative to a vacuum unit. They are smaller, very positive in their action, and as an added benefit for a hot street rod, they won't be affected by a lumpy cam and it's attendant vacuum problems. I am seriously thinking of one for my old truck when I start rebuilding it; the power steering pump will be there, so why not?!