Hoppy,
Your
oil leak is most likley from the
oil galley plugs at the rear of the block, on either side of the cam plug. This is also under the block cover plate of your scattershield. Bummer. This is the same leak I have.
I also have the same fuel system as you and the electric must run full time to feed the mechanical. I have the Carter on the block and a Holley orange [7 psi] electric. The system works fine full-time and cold starts don't kill your battery after a long no-start period when you lose the fuel head. You also won't need a tank return line if your floats are set correctly. Don't think you want to drill the tank and weld a bung. You also don't want to plumb it to the fill pipe vent lne.
Put a cat pan under the motor until teardown time, [I did] and drive the a$$ off it, [I do]
Best luck,