Note that GVWR is ONLY for a vehicle WITHOUT trailer. And, yes, this is true in all state and federal statutes. Like I said, there are more calculations that are required for trailers but the average person is unwilling and/or unable to do them. It comes down to axle spacing (moment appiled about the loaded axles) and weight per square inch of tire contact. That is why I suggested you do a free body diagram. The actual load becomes a function of where the load is in the trailer. This is why most horse trailers have the horses just in front of or on top of the axle. There is no moment applied to the rear axle of the tow vehicle.
And this is why there is pretty extensive software to make the calculations. The over simplification is the calculation I presented which anybody can do and overestimates the load limit, thus applying a factor of safety.
With a trailer, the vehicle ceases to be a two axle truck. It becomes a 4 or more axle vehicle (for most horse trailers). Thus the loading per axle becomes a function of moments and direct loads. Hence why my 4,500# trailer only adds 750-1,000# when hooked, and not even coming close to the GVWR.
The physics doesn't lie.
Take the extreme example of a semi that hauls 100,000#. Do you think the tractor must have a GVWR of that?? No truck on the highway does.
"The GVWR includes the weight of the vehicle itself plus fuel, passengers, cargo, and trailer tongue weight." Which is EXACTLY what I was saying before!
Also, "The GVWR is not the same as the unladed weight, gross combined weight rating, towing weight rating or registered weight rating."
You are beginning to make my point for me. Do you actually read the references? Your second reference is completely wrong according to your first reference.
Now the GCVWR, "Gross Combination Weight Rating or GCWR is defined as "the value specified by the manufacturer as the loaded weight of a combination (articulated) motor vehicle. In the absence of a value specified by the manufacturer, GCWR will be determined by adding the Gross Vehicle Weight Rating (GVWR) of the power unit and the total weight of the towed unit and any load thereon." This is stipulated by law and can be found on several trailer manufacturer web sites, if you don't believe me.
Thus GVWR is NOT absolute as stated in your second reference.
According to Ford Motor Company, the GCWR is calculated by adding the following weights together: The vehicle's listed curb weight, allowable payload, driver and passenger weight and trailer weight. It is the combined maximum weight limit that the manufacturer has set for the two vehicles once attached.
My 7,000 pound truck is EMPTY except for 2 passengers and full fuel tank. Once the loaded trailer is attached, the weight goes UP. I never denied that. But you are not "listening" and trying to understand how one calculates the actual payload capacity of a combined rig. The manufacturers know this and design accordingly.
For example, my commercial hay hauler uses a 1-ton to haul 35,000# total combined weight per the DOT scales with no truck issues and within all legal limits.
If you were in Europe, where perpetually they haul horses up the Alps with their little Opels leaving me goggling out the window on the autobahn going, "...HOW...?!", probably you could.
Here in the States, where the laws of physics apply, no.
You don't just need to move it, you also need to stop it, and turn it.
Btw, why are there several exclamation points behind "2007" in your OP? My Dodge 2500 is a 1999 that I purchased for $3,999 with 80k miles on it and it has, knock on wood, been fabulous. I haul with it all the time and have several times done 12hr -24 hour round trips to go to clinics or move a horse somewhere. Get a well maintained old truck and you will get a whole lot of truck for your money.
I have this same truck and haul a 2 horse SL. However, I previously had a nice Merhow, also 2 horse SL with a dressing room and basically the truck couldn't handle it. The 2H I now have is aluminum on a steel frame, no dressing room and only weighs 1700lbs (no load). With 2 horses in it, it hauls and is OK, but I certainly wouldn't want to do anything long distance and it's not effortless.
I have a newer version of that truck, which has a higher towing capacity, and it's great for my towing needs - two horse trailer with 1 WB in it, local/flat towing only. Wouldn't even consider trying to haul something heavier...
In the depths of time, the words uttered by early man as they leaped for the first time onto a prey animal with a brain the size of a golf ball, were undoubtedly, "Hold my beer and watch this...!"
It wasn't really enough to haul my 2H stock trailer with one horse in it and I pretty much destroyed that truck. I gave it to my brother and he had to get it inspected to get it registered and told me it bombed the inspection. In MD, you only have to get it inspected at purchase time. I hauled with it less than once a month, average.
So, no, I would not go with a 1500 for a 2horse with a dresser
I hauled my 3yo wb to the trainer with my hubs 1500. I normally drove a dodge dually with the HO cummins and a 6sp. I had left the truck and trailer with my mom for her horsey vacay so I was left with the baby truck and a little circle j 2 horse slant stock trailer. I have logged a lot of miles with trucks and trailers and let me tell you, it had me in a near panic with just one horse and a light trailer behind the 1500.
Beyond the lack of power of the motor, horrid fuel mileage and not enough stopping power, you will be wearing out parts by putting so much strain on the truck. Tranny, rear end, suspension. It's just not worth it.