i am loving my 37's and 4.10's in the f350. powerstrokes tend to operate better at higher rpms than cummins though.
I have a healthy 1997 Cummins/NV4500 4x4 with 4.10's and 37" MTR's. The truck put down 338HP and 797Ft lbs torque at the rear wheels on the 37's with really basic mods, that said I love my 4.10's and regularly pull long distances at around 20,000 lbs. That's my Dodge, my 1 Ton Tacoma,10K capacity trailer, slide in camper, a bunch of extra fuel, tools and parts. I don't think most people would really notice the skip from 3.55's to 3.73's I'd say go to 4.10's and don't look back!