[comptiger5000]

Considering that mine will effortlessly accelerate at 1/2 throttle from 37mph at around 1100 rpm in OD with the TC locked, I'd say I could gear it A LOT taller and still cruise comfortably. It's only at 1050 fpm turning 1760 rpm at 60mph now though.

I figure I could probably be fine with throwing a gear vendors on it and turning about 1370 at 60mph. It would need to downshift on most hills, but it should pull fine. The 4.6 Ford doesn't have a ton of low end torque (especially in car applications), so 1300 or so at 60 is probably the lower limit before power drops off too much, potentially causing it to be running under enough load to hit fuel enrichment.