I started my conversion to an external fuel pressure regulator with a return line and thought I would share some info on fittings.
1) The port that the in-the-tank FPR fits into is almost an exact fit for a 1/4" NPT pipe plug. It fits pretty tight, but I coated the threads with epoxy just to be sure.
2) There is enough room for a 1/4" NPT street elbow for the fuel return, but there are reinforcement ribs on the underside of the plastic housing that must be taken into consideration. In other words, drill your pilot hole from the bottom, not the top.
My FPR arrives tomorrow, so I have overnight to decide if I'm just going to hack into the line, like Evo did, or make a proper distribution block with the MCX add-on injectors in mind.