any way to add fuel filler to passenger side of 2005 f150 xlt 4x4 35gal tank pu?

Look up Ford F150's built in Europe and see if there is a part number cross reference. Can you put a "piggy back tank" in the truck bed or modify the exhaust, bed side sheet metal for the filler door, fuel lines for the connector to the original tank and add another fuel gauge for a tank behind the rear axle ? Go to Ford for the "European design tank", "Tractor Supply" or "JC Whitney" for a "piggy back tank" that would mount in the bed. With the "piggy back" design you could set up a fuel line (with shut off, don't want to mistakenly overfill) to the tank in the chassis or just pump from one to the other electrically or by hand. They make units that fit in the bed in front of the 5th wheel hitch (if that is what you have, but remember to decrease your tow rating by the weight of the fuel tank "filled", so you don't overload the brakes or the leaf springs). What about just replacing the tank you have for a larger size unit ? I think the cheapest and quickest way thru this would be to mount a "piggy back tank" in the bed (as it can be transferred later to another truck) and a hand pump ($35) to transfer fuel from the piggy tank to the chassis tank BUT REMEMBER TO DO THE MATH ! Get the "full weight" of the tank so you can subtract that weight from your allowable "tongue weight" or rear axle load carrying weight, so you can decrease the load allowable on the springs and protect your rear brakes (Don't want them over heating).

you can maybe through kits online but chances are your going to be drilling and making it yourself which isnt safe when it comes to gas