A great set of advice, as he knows more about gph
than anyone else I know. But some more info about this is needed before I could even attempt to run anything. I'll go over the basics though.
Basically, you want a return pump rated much higher gph
than your overflow. You want as few bends as possible in your piping, mostly staying away from 90 degree angles. If you get a return pump that is, say, double the gph
of your overflow you can simply install a ball valve right on the return piping. This will let you not only perfectly adjust the flow rates to match, but it has also been discussed that doing so can actually increase the life span of pumps...though this isn't something I can directly confirm.