Hydroboost brakes....

I'm not sure if the power steering pump flows enough volume to handle both the hydroboost brakes and power steering roles. It probably wouldn't be overly difficult though, since 96-04 had hydroboost, so you could salvage a lot of stuff from those years and just need to fab up some hoses. If I'm not mistaken, some Lincoln Mark VII's came with hydroboost, so that's another potential source for parts.
 
PS pump flow shouldn't vary that much I wouldn't think. My '81 Olds originally had a diesel engine and therefor had a hydroboost system with a small capacity PS pump.

Thanks Matt...I'll start lookin into the Mark VII's for options. Wonder if I can just bolt the newer pump to the factory 5.0 bracket?
 
The powersteering pump should pump plenty of fluid. I've talked to a few guys online who have done this conversion. However, there is really no reason to swap it over to hydroboost, unless you are running a really big camshaft, and the vacuum booster isn't doing it for you anymore, like in my car. I did some research on it, decided it wasn't worth it, and swapped my car over to manual brakes instead. Not sure if that was a good idea either, but that's what I did.

Anyway, you need to get the booster and master cylinder from a 96'-98' Mustang. Then you have to have power steering lines custom made at a hose shop. It's not terribly expensive. I also believe you have to rebend your brake lines from the master cylinder to the proportioning valve, as the hydroboost master cylinder sits farther forward in the engine bay.

Kurt