The confounding 3/4 ton truck...

So, I'm genuinely curious and asking. Can anyone point me to a reliable source that can explain these issues and parse the considerations? Knowing that any rating is limited by the weakest link in the chain, is there someone that can express how to know which elements should be considered? I understand the reasons for the arguments people make in these questions, but I've never seen anything but personal opinions. I'm just wondering if there is more definitive information out there.

Wow...your asking for a lot from just one document.
Points to consider.
1. first you have to find what are your legal weight issues for any vehicle.....not just a 3/4 ton truck. Legal issues are safe issues. Most rv owners are clueless of what safe/legal weight issues are for LDT trucks. Your local state troop command post captain or a commander is the best place to start. These guys are your experts and if he can't answer your questions he will have troopers on duty who can answer them.

2. Next is what our truck mfg tell us about their trucks mechanical specs. The best example I can think of is Fords Fleet body spec website which gives us all Fords weight specs and more importantly actual mechanical specs of all the standard equipment and options regarding the vehicles ability to carry weight. GM and Dodge/Ram needs to take a lesson from Fleet Ford on this subject as they don't have a website with all the specs one document.

Weight issues on rv websites stems from the many blogs around the net mainly from rv folks. They say things like gvwr is your legal vehicle gross weight....or the yellow payload sticker is the legal payload when in fact their not...anywhere. Even the clicky posted above is no legal weight code but as it says its a simple worksheet. NHTSA has much the same document...but its just another guideline or recommendations.