Just did what you are about to do.
I used a 750 gph with a ¾" outlet for deep bilge
3700 gph 11/2 " outlet at higher level
30 Gusher manual
2 buckets
Each pump has its OWN separate intake and discharge hose.

Not much I to suggest except do a group search. It aint rocket science.
Lots of valuable info found here if take time to look and read.
However....I do recommend using

1 ½ " pvc "SUCTION" hose. Its found anywhere for about
$1.20-$1.80/ foot. Go to a farm supply or contractor supply or home
depot. Do not even think about saying marine bilge hose! The wine
industry use it too except that stuff is USDA okay and lots more
expensive. "Trash pump suction hose" is what ya want. Its very tough
with hard plastic spiral. Very smooth inside. Also clear. But some
folks would say that algae will grow inside. Has not happened to me.
Besides I like the idea of a fast visual assessment to find an
obstruction in the system.. Don't forget the vented loops.
Still Bobing thanks to suction hose.