The holley mech pump on my old car had a distinct inlet and outlet that you couldn't just change by swapping fuel lines. I just removed the 10 allen-key bolts from the underside of the pump, then clocked the base to the angle I needed (you have about 5 or 6 positions available that don't foul the inlets/outlets against the motor)
CAREFULLY retighten the 10 bolts - the metal quality isn't all that great, and I've seen the threads strip in the upper section of the pump body..... OK, OK...I stripped one!!!
Just don't tell anybody
It's really easy to adjust the angle of the inlet/outlet, just make sure there aren't any leaks before you drive the car again.