I was apparently thinking of the pressure OUT.. 40 is a low reading to the box.
Off topic but related, the '87 GM TSM lists the following specs for Chevy PS pumps (truck versions):
GPM min/max: 1.32/3.1-3.5 relief valve settings: 1200-1350psi depending on the pump
you will want to know this when you're setting up hydro assist.
anyway...