gas leak?

[vtwinsport]

Hey all, updated this original question below;

Got a problem I've been monitoring.
Problem is 7 miles per gallon. So, why such low mileage? I've heard 12-14 is usual.

First of all, its a stock 350 crate on 76 2wd frame with TH350. New edelbrock carb with phenolic spacer, intake and headers. Running good and shifting well. Not getting any flooding or smoke upon startup. More facts; only the passenger tank on it. all extraneous multi tank stuff is gone, sender is two outlet, one to the pump, other is vented along the bottom of the bed. I can't find a leak anywhere or anytime- sitting cold or while idling.
Pressurized the fuel supply by plugging the vent hose. Ran at idle for a few minutes, then checked for leaks while idling. Not a drop anywhere. Wiggled some fittings, moved hoses etc but I couldn't find a leak.The system, including tank, was well pressurized indicated by the small amount of gas that came out of the filler neck when I removed the gas cap while idling.

So, my next questions are; does my fuel pump diaphragm have a pin hole leak, passing fuel into the oil? And if so, any way to check that?
thanks in advance.