My system is similar but different, with two low pressure pumps and no selector valve.
Both low pressure pumps feed the swirl pot, but the return path of least resistance is to the driver's side tank (as Ian recommends, right next to the pickup). I typically run the driver's side pump which runs down the driver's side tank, and when it gets "too" low, I run the pass which continues to supply the swirl pot, but also replenishes the driver's side tank. This saved the valve and connections, etc... Just need to be careful not to continually run the pass side if the driver side isn't empty.
As stated, both these fill the swirl pot. A high pressure pump draws from the swirl pot (~4 gal, so very little opportunity to induct air into the system unless you're REALLY low on gas), and this circulates to the fuel rails and pressure regulator on the motor, returning surplus fuel to the swirl pot- which also allows it to cool a bit.
Sounds like our builds are similar, I have the
M-6007-X302B from FMS which is also a 302 with a mild cam, 345hp/345tq. Matched with a ZF box, it's a great combination. With the fuel injection (mine is Edelbrock Pro-Flo), it runs fantastically**! You'll love it.
Chris
** - While cruising home one night last month after dinner with a friend, my EFI ECU died on me with virtually no warning. Right up until then, it had been flawless. Despite Edelbrock no longer supporting the version I have, I have found a new ECU on the second hand market and am trying that. If that doesn't work, I will upgrade to a newer system. The performance and driveability of the motor is truly fantastic. It is so worth it. PM me your number if you're in the states and I'd be happy to chat about it with you.