My rig is a 2003 Dodge 3500 srw short bed pulling a 4 horse Elite LQ trailer.  12' SW LQ 29 feet on the floor, 37 feet overall.  I recently weighed my rig to see how heavy I was on the rear axle of my truck. My truck weighed 7200 lbs and the trailer 11,500 lbs.  This was with most of the gear in the trailer, but no horses or hay in rack.  With the trailer hooked up my rear axle weight was 6450 lbs.  My load range E tires have a weight rating combined of 6400 lbs for the rear axle.  I realize the best combo for this trailer would be a dually, but I am not able to do it at this time.  I have pulled this rig several thousand miles in the last year and it handles it ok, but I was always concerned about rear axle weight.  Some questions:  1. Is there a tire out there with a heavier rating than I currently have? 2.  Are the axles or rear end any heavier in a dually or you only gaining the additional load capacity of the extra tires.  3.  I have a B&W turnover hitch and was suprised that only 150 lbs of the 3700 lbs pin weight was transfered to the front axle--is the hitch positioned farther foreward in a long bed truck to transfer more weight.  I dont think horses would add much to the pin weight because they are centered over the axles and the hay rack is behind the axles.  Thanks for any advice.

True, alot of folks that use slide-in campers and tow, go to the Rickson Wheels (http://ricksontruck.com/). They are a conversion to 19.5" wheels with 14 ply tires (G). There is a reason the truck manufactures are going to taller tires (17-20) besides looks, the larger tires can have a higher load capacity. Your year of Dodge is the first year for Dodge to use the American axles from the Dana's. They seem to have held up well. Of course if you weigh your truck with the horses and hay, you know how much over you are. I've been overloaded my whole towing life, but that isn't for everyone. I feel safer overloading a heavy duty 3/4 ton or higher than a 1/2 ton. But with live tall animals it's prudent to be 15% below your trucks capacity. Surprised your front axle percentage is so low, most in-bed hitch companies use the existing frame holes and end up 2 to 5 inches ahead of the rear axle. I've noticed with diesel crew cabs, having the hitch over the axles isn't as important as a singe cab gas engine needing steering weight from the tongue weight.

On Ford, a F350 dually has one size larger Dana axle and larger brakes than 350 srw but same springs. GM has more springs on the dually, Dodge has thicker springs on the dually.

My book shows 9350# for rear axle and springs on the 3500. It shows 6150# for the 2500. Your GVWR is 9900#. Dually and SRW have E rated tires with less capacity per tire on dually but of course more tires. Duallies have advantages with braking and handling curves, but as a careful driver, it sounds like you are ok now.

Something to think about next time you upgrade trucks. Duallies cost fuel economy and are a pain in parking lots. You could consider a Hell-Ya hitch helper, http://www.hell-ya.com/ I use mine to review IRS SUV's when I can't use a WDH.

I guess I will stick with the SRW truck for now.  I have enough trouble out West hunting getting through some of the small roads without having a wider truck.  If I ever weigh the whole rig, Ill let you know.  Fully loaded, I'm sure it's close to 24000.  I was hoping someone would know about a 17 inch G rated tire I hadn't heard of.  As far as the MFG GVWR, I know they keep it low on purpose to keep it below the 10,000 lbs that would put the SRW trucks into the Commercial class if used for business.  I put Timbrens on the rear of the truck so now the overload springs barely touch and the rig sets level and handles very well. 

As I am in law enforcement and inspect commercial  vehicles as part of my job, I can tell you that here in Minnesota we do not generally enforce the manufactures ratings as they are that, just the manufactures recomendations.  We use the MFG GVWR as an indication of weather the vehicle is heavy enough to be a comm. veh and the type of license required to drive it.  I think the tires should be kept in good condition as to age if a person is going to go over the weight ratings at all.  I feel ok with the rig I have, and have put about 7ooo miles on it in the last year with no problems.  I don't think I would run it with 5 or 6 year old tires on the back that were weather checked.  I looked into the Rickson wheels and read nothing but good things about them, but the price is too much for me right now.