i have 3.73 in a 04 f250 6.0psd, 4x4, no tuner
i have 4.10 in a 99 f350 7.3psd, 4x4, drw, no tuner
i have 4.88 in a 99 f450 7.3psd, 2x4, drw superchips flashpaq
no doubt about it, the 4.88 gets a load rolling EASY.. it just can't do over 75 without getting too close to yellow rpm.
the 3.73 has been fine for towing 7k and 10k loads all over, mountains and all.. go heavier, and you feel it.
the 4.10 for me seems to be the happy medium. I can still cruse interstate speeds with everyone else and not get too close for comfort to yellow rpm.. yet drags 12k like a half ton pulls 5k.
My only gripe? All the goodies are on the 450.. exhaust and intake upgrades, air bag suspension, top air scoop for towing taller loads, multi gauge cluster upgrades ( pyron , extra temps, etc.. ) upgraded ps cooler and trans cooler, rear end upgrade, auto xfer aux 50g fuel tank..e tc..
She's my go-to for towing non interstate.. :) if she had the 4.10 and was 4wd.. I'd be in heaven. :)