I have one custom fuel cell for all of my fuel (most likely racing fuel)
i then come off of the cell with two -10AN fuel lines both feed through inline Peterson fuel filters. one line goes to a Aeromotive 11203 SS fuel pump for daily driving under normal pressure. The other -10an line goes to a Aeromotive 11202 A2000 pump for strip use. Both of the lines have a one way check valve and feed into a y fitting and then a -10 AN on to the regulator.
From the regulator on i have -8AN lines to the carb with a return line back to the fuel cell.
I would show pictures but i have not installed it yet, i have all the parts though.
I understand what your trying to accomplish, you may want some check valves here or there if you want to keep the mechanical pump.