I did use the 6 cyl power steering pump. I had to use a different p/s pump pulley. I also shortened the return line connection on the bottom of the p/s pump to clear the frame and had to put a 1/4" spacer between the p/s crank pulley and the alternator/water pump crank pulley.
I think I needed the spacer because I have a Z28 p/s bracket and non-Z28 pulleys (not because it's a 6 cyl pump). I believe the Z28 pulleys have deeper grooves and stack up thicker than the "standard V8" pulleys on the crank. I think the Z28 crank pulleys and p/s pulleys are NLA so I'd try to stick with "standard V8" brackets AND pulleys. You can find these pulleys in the aftermarket pretty easy - black, chrome, aluminum, etc.
I had a lot of problems trying to get this setup to work out and I never really figured out exactly where I went wrong, but it the 6 cyl p/s pump does fit perfectly in the V8 cradle bracket. Maybe someone else can confirm/deny my Z28 pulley theory.