If starting from scratch, I would install 2 electric pumps. For the first I would get a small pump with the smallest diameter hose fitting available. I would install this pump in the bottom of the bilge. This first pump will run anytime you get water in the bilge and with the small diameter hose you will get less backflow into the bilge when pump shuts-off and keep your bilge drier.
I would then install the largest pump that will fit, as PB suggested, on a stand or platform about mid way down into the bilge. This second pump will be available to do the true heavy lifting in case of major water intrusion. This is a method that has been suggested by a number of different authors, in a few publications. Seems to represent the best possible solution.
Maxum 3200 Miss Adventure
Formerly - Tartan 34C Yawl