I came up with a solution to my twin fuel tank dilemma - sort of. I found a bunch of listings for 'dual fuel tank switching valve' and they all appear to be either 3 port (one in/two out) or 6 port (same - doubled up). The vast majority of the 3 port valves are identical (they look like copies of Ford and GM OEM fuel tank selector valves) and the prices can be vastly different (from $25ish USD to $50ish USD) but as always the freight is brutal. It will eliminate the need for 2 pumps, should simplify the install but the part is specified for a non-return line fuel system and the selector valve must be installed with filters into both inlet ports from the tank - that means the pump must be installed in the main fuel line after the selector valve. Not ideal with an electric fuel pump.