There are two completely differant pumps being talked about here Both are Perry/varsane/conley and they are of completely different operation principles and plumbed in different ways.

The VP-30 regulatiing pump uses a crankcase pressure tap to provide the pumping action and will have three nipples to be plumbed which includes the pressure tap to the crankcase.

The small VP-20 Ossilating pump has only two nipples (in and out) and there is no pressure regulator. Its pumping action comes from a tiny bouncingball and the pump must be mounted in the plain of crank rotation on the crankcase for best performance. The pump is between the tank to needle line and if avaliable muffler pressure is also used.

Villa I beleve the small ossilating pump would be preferable for your installation. I have been able to successfully use 50 ounces of fuel in three stacked tanks on a forty size airplane using the ossilating pump and muffler pressure.

John