I have been dealing with an issue like this on the '68 Mustang EFI conversion. I am running an electric pump right next to the fuel tank and below the top. On long steep grades and especially at high altitude it vapor locks and quits. Cool it down and away we go.

Ethanol fuel is the problem. We are supposedly going from 10% to 15% which will make the problem worse. Only solution I see is something like the Tanks Inc PA series fuel pump -in- the tank.

any chance of adapting the selector valve setup from your mid-late 80's f150?

these were return style fuel injection with two tanks from the factory.

just asking the question....

couldn't you just put the pump between the tanks so its about 20" from both tanks?

personally, I do not like the dual tank setup, and if I was going efi I'd keep it single tank. As stated, 38 gallon tank would be a great option, JBG sells one that bolts into your truck in the rear tank location.