The actual engine fit might happen, the turbos are low mounted making the package kinda wide which wouldn't be a problem on the F150 but may be a problem on the narrower Mustang platform, not sure it would clear the frame rails and strut towers.
I was really referring to the electronics, you would have to run the engine on the truck computer and then tie that into the Mustang body electronics, things have come a long way since the A9L / A9P computer days, pulse width modulation, multiple TCC lockups, it takes tuners several attempts to get shift pattern correct on a car that has been out for 3 years already, I would think it would take an electronice genius to get that package to work. Easier to turbo the 3.7, I built my kit from scratch over a few weekends, rough tuned in a few hours, made more HP than the 3.5 did with under 13 psi (444 rear wheel)
How so? The base engine for the F150 is the NA 3.7. The 6 spd. automatic tranny is standard in the F150...probably geared different though. But the truck tranny mates to both the 3.7 and the 3.5. If the Mustang's transmission is different from the truck's, it still bolts up to the 3.7 and might do the same on the 3.5.
If the 3.7 goes where the 3.5 goes, can't imagine the 3.5 Eco couldn't be made to fit in a Mustang...if you had the whole package.
Been ages since I did an engine swap though, so might be overlooking something. Educate me.