Just note, that the actual model pump in your link, is a bilge pump, and will not work.

You would gain some flow rate increase, but those .75" fittings are always going to be the bottle neck, and create head pressure. IIRC, I think that pump's outlet is 1.5", so you will have to upgrade the outlet hose and manifold inlet. You would also likely want a 1.25" intake at least.