I wouldn't buy the hose until you have the pump and brackets. Do you have a pump now? Do you have brackets now?
You installed a 70 up aluminum water pump.
A saginaw pump was installed in a V-8 application in 70-72 A-bodies. You need to find the pump and pump brackets off one of those cars. Question is, is when you switched to the alumunum water pump did you switch (or is their a difference?) to the 70-72 water pump, alternator and crank pulley.
Or contact Buchillion and see what to see what pulleys go with the pump bracket they sell.
Many times these cars are tossed together with whatever seems to fit thats laying around.