dvsdev
+1y
I put a FPR on my recent weber install, I checked to see what the pressure from the factory mechanical pump was, mine was just over 6psi, weber recommends 2-2.5psi so I would run a reg regardless of being factory mechanical or electric fuel pump.
I also plugged the carb return line, option I did was pull the fitting out from carb, cut off barb, fill the whole thing with solder, refit fitting and re-sealed around the fitting with a fuel safe thread lock solution.
Depending on your setup, if you have a good inline filter you could just split the fuel inlet hose and fit to both carb fittings, looking at them they both hook-up before the needle anyway so it should be all good... Should be.