I would agree with those here that said you'll be ok. We used to have a '99 F250 V10 but we had the 4.3 gear ratio and we towed everything from a 25' TT, 29' TT, 32' TT, and it did fine, with plenty of power to tow these, and that's with the 32" TT being close to 10K. When we upgraded to a 35' fifth wheel with a GVWR of 14K, although we never towed to full capacity, the truck struggled, really struggled. Our mpg was 7 - 9. Since then we have upgraded to an F350 DRW Diesel and all is well again.
2011 Bighorn 3055RL, 2011 F350 DRW 6.7L 4x4 Diesel Lariat and Hensley TrailerSaver BD3, 1992 Jeep ZJ and 1978 Coleman Concord Pop-Up for remote camping
Dave & Renee plus (Champ, Molly, Paris, Missy, and Maggie in spirit), Mica, Mabel, and Melton