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When I installed an ITP Diesel Fuel Tank/Pre-Pump Kit, I discovered that the little umbrella was completely broken off and the pickup tube crumbled when I started handling it. I replaced the whole mess with a piece of 3/8" brake line from NAPA. No problems so far.
The pickup line from the tank is 3/8" where it hooks to the plastic "hose" with the quick disconnect. The "hose" and all the line up to the pump is 5/16". The return is all 5/16'.
I think Ford made the tank connections different sizes on purpose to make them "idiot proof."