The actual pumps are all the same. The external reservoir is designed to fit a specific motor be it a Chevy; whether a small block, big block or 409, or it could be an Olds, or Pontiac series of engines, etc. as all GM cars used the same pump. The pump's hoses are also specific to the car body which could be a sub compact, economy car, sports car, mid size, or full size combination, front or rear wheel drive. The pulleys come in two flavors: bolt on or press-on, with either a single groove or double. The hoses are also specific to each body and motor combination. Similarly there are two sets of small block power steering brackets one set for short water pumps and another to fit a long water pump.
You can easily find the pump at RockAuto, but the mounting brackets are a different story.