Check out the page at Documentation/Fuel Systems/Fuel System Part #'s/Fuel Filler Pipes. That will give you the part number.
You may ask why I can't just give you the number. When you look you'll see that we'd have to play 20 Questions given all of the parameters involved, so it is far better to let you figure it out as you know the answers to the 20 questions.
Gary, AKA "Gary fellow":
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Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI