I find a bolt the correct size & a little longer with a section of unthreaded shaft. Then I cut off the head leaving about 3/4" of plain shaft, then cut a slot in the end for a screwdriver.
If the bolt you selected has excessive thread you will also want to shorten that end to about 3/4".
Now you can screw this "pilot" bolt into the hole that is easiest to access with a screwdriver. This will allow you to slip the pump into the correct position over the pilot & keep it there with 0ne hand while installing the other bolt. When the other bolt is snugged you can remove the pilot & install the other bolt & snug up everything.
Long explanation I know,
couldn't figure a brief way to s'plain
Craig