Found this 34 pg acrobat file on a GM web site a few weeks back, shows and tells how to spec a class 4 and larger truck, for both HP, torque, gearing, ie tranny and axle gears, to do what YOU want your truck to do performance wise. Look it over, I think most of you will find, if you put info to use on your rig, being it a class 1-3, ie half to 1 ton trucks to 12,500 lbs GVWR, you will have a better understanding of what goes into figureing out GCWR ratings to a degree.
Dave G's site is a good starting point. There are links that deal in greater detail.
Here's where to find the best tongue weight information. http://www.sherline.com/lmbook.htm
www.trailerlife.com how tongue weight can be greater than what you know.
There is no easy determination for length. More than 30 items on both the trailer and tow vehicle would need to be considered to find the actual length limitation one could tow. The bottom line is does your vehicle have enough resistance for any wind force the trailer applies.
The best tow vehicle is a pick-up and the best trailer is a fifth wheel or gooseneck. The resisting weight is in the best location, the location of where the force of the trailer is being applied is the best.
I just looked at the link for..."Warped brake myths and truths"
As a long time auto repair person, doing significant work in the field of brake repair on both cars and RVs, I can say HOOEY!
I have seen a LOT of warped discs. Still proper break in and use of brakes will give you more pulsation free life from them. Use engine brakes, gear down, and don't drive like a cop, and your brakes will last longer. If they warp, you MIGHT be able to turn them once, but replacement is best. make sure the brake tech mounts the rotors on clean rust free hubs too!. I'll get off the soap box and let you get back to the matter at hand. (Sorry)
Looking for a new tow vehicle for a 5000 gvw trailer, I'll use your good info here to help me find one.