I had a 5.4, not what I expected,, bought a 2004 F150 HD (towing package), supposedly Fords truck of the year!!
Again, NOT what I expected!!
2004 thru 2007, 5.4 had issues with Cam Phasers, and spark plugs, othe F150 body style issues also,,(bed rusting)(rear end clunk and clatter)(weak transmission).
Also Super Duty had similar issues same motor..
I would steer clear of any motor Ford produced from 2004 thru 2007.
A good one will have allot of miles on it, those are not common but they are out there, Now lets not get into the Power Stroke,,,,,,
Research via the internet,, search Forums,, F 150.net, F150.com, Superduty.com,, ETC,, I got in trouble voicing my opinion on D--ge here,, But you have to research then go drive 'em..
Have a drink and sit down,, Google D--ge V10,,F--d 5.4 reliability and you will form your own opinion on what you are looking for.. Good luck, the top three manufactures are not cheap,, but you want reliability!! Economy is a grey area,, My thought is,, if you want economy,, buy a small car,, if you want a vehicle to work for you, do some math,, weight to HP ratio, weight to mass, ETC..
3/4+ ton trucks do not post fuel economy for reason!!