These pumps are not fussy about orientation, as far as I know.
You need to isolate the vibration, otherwise the whole chassis will buzz when you turn on the ignition. When the engine is running, the engine noise will hide the fuel pump buzz, though.
One way to do it is to use 2 or 4 exhaust bobbin mounts to mount a metal strip, and jubilee clip the pump to it, Like this:
I made an Ω-shaped clamp out of a 2" wide strip of aluminium, and used felt to mount the pump in it. No picture of the pump mount, but here's a general idea where it goes in the car:
