The Saginaw steering gear box you have was used from 1965 up to 1999. It wasn't used in 1964 so it isn't a bolt on swap. One problem you will encounter is the difference in size at the end of the steering column. The two steering gear boxes have different size and shape input shafts. The aftermarket sells a special rag joint to bridge the two.
Since it may take a while for the members who have actually done this swap actually respond to your request for help. There are also several articles that I have read on line at Source Interlink Media's web site (you may know them better as Hot Rod, Car Craft, Super Chevy, Popular Hotrodding, or Chevy High Performance magazine). These articles show examples of installation of modern power steering boxes on several different cars including a 1964 Chevy. That is how I knew you need to retain the Pitman arm off the Camaro steering gear box because it is smaller than the one used on the Impala. They also list the parts beside the rag joint you will need and where to buy them (most car mag articles are little more than disguised ads by the manufacture to highlight their product).