What do you tow? That could help. If you are under 10k, then I think you could do 3.55's, but anything heavier and I would consider the 4.10's. I am surprised they don't offer the happy medium 3.73
2017 F-350 CCSB 6.7L
[old]2002 7.3L PSD, 6spd, 4x4 Off-Road, Super Cab, Short Bed, ARE Topper, SCMT Autometer gauges, Tymar, 4" SS aero-turbine exhaust, & WW.
'73 Bronco 351 SEFI, 35's & Locked!