Newbie and can't figure out the "What can I tow" math

3:42 is not ideal, it will struggle at times, however, it will work alright with that trailer for a while. You'll be within 100 lbs of your payload rating so for better towing performance, plan on traveling with the tanks empty. A 3.73, 4.10 or something along those lines would be a lot better, but that's probably a $1500.00± cost (if even available).