Gear ratio question

[Behr]

Im wondering what for a gear ratio i should switch my 04 f350 to. im currently running 3:73s and 315/75/16 toyo mts and im putting on a set of 38/13/16 michelin xmls. the truck is a daily driver as well as i use it for work pulling cattle trailer with atleast 10-15000lbs loaded so i need this truck to be able to do this once i swap the tires. also the michelins are almost double the weight as they weigh 115lbs and the toyos are only around 70lbs. any input and advice is much appreciated

[PGreenSVT]

I'd put a set of 4.30's in it towing that much. Some might even suggest 4.56's but I'd go with 4.30's if it was me.