michael,
v8 or 6 cylinder??? the 57 gmc used a 347 pontiac v8 or a 270 gmc 6 cylinder. The six cylinder had a tandem generator power steering pump. The v8 had a seperate power steering pump with a huge pulley.
gmc used a different power steering setup than chevy. the gmc used a speacial saginaw power steering gear for the years 1955-1959. they are very tough to come by and fetch a large price when you do find them. they also used a different steering column that was coupled with a borguesson (hope i got that right) joint.
There was an optional hydrovac breaking system used on gmc trucks. I don't know much about them other than they had a hydrovac unit under the hood on the firewall on the drivers side, and they utilised a rather large reserve vacuum tank located under the floorboard on the drivers side.
