Chris, any thoughts on swapping an Eco Boost V6 in place of a 5.4? They seem to be decent motors, just very under powered or maybe under- tuned, if that is a word.
A stock 3.5L V6 Eco Boost makes 365 HP and 420 TQ, with good area under curve due to the turbos. A stock 5.4 Triton makes 235 HP and 335 TQ (up to 2010) and then 310 HP and 365 TQ from 2010 on due to a new head design IIRC.
As I am sure you are aware, very basic bolt on components for the Eco Boost will yield appreciable gains. (Full Race Stage One Package)
Final Result of Test 1 (add Tune only): 421WTQ and 347WHP Gains: +125wtq/+70whp @3000rpm and +75wtq/+60whp @4000rpm
Using a 17% driveline loss for a 4WD truck, that gives you about 420 HP and 500 foot pounds of torque. I would not expect diesel MPG, but gas is cheaper than diesel in many places. The 7.3's whilst loved dearly by many are 15+ years old now. In that time, massive improvements have been made in turbo gasoline engine tech by the OEM's. Just a thought in a case where a customer may be considering a majour overhaul or a diesel rebuild (7.3 or 6.0 fix)