I just traded in my 2013 F250 6.2 with 3:73 gears for an F350 Diesel :B currently towing a Jayco 256RKS TT (GVWR 7600 lbs). The 6.2 gave me 16.5 empty on the highway, 13.6 overall combined HWY/City, and 7-10 towing depending on the terrain/wind.
I loved it, and it did a fine job towing the TT, but we are moving up to a 5er, which is why I changed. The only caveat in hindsight is I would have ordered and got the 4:30 gears. It was not, however my daily driver. If towing 8K or less, and you're driving it a lot, the 3:73's work fine. Good Luck.