'What can you fill a barrel with to make it weigh less/'

Changing the springs will not change the rating, but likely will make it carry the load better. How are you on tire ratings? Unlike GVWR, it is against the law to run over tire rating. How about axle rating? Part of that rating is the amount the brakes on the axle are designed to stop...

Its not that it allows more to be carried but let's it carry the weight better

May level the truck but won’t increase payload.

Please, show this retired cop any law that says it's illegal to "run over the tire rating" as it pertains to us RVers.

Where do I find Tire ratings?? BF Goodrich ~ All Terrain lt625/70r16 "E" max psi 80 Apr/2018 Question on that Tire shop says never run more than 40 ~~ Mechanic friend says 75 another says 50. I will be getting truch weighed all 4 corners soon.

~~GAWR FRT (3500lb) with265/70r16 32psi cold ~~ Rear (3760lb) 33psi.

Does any of that help

Thanks for your time & insight

The only tire ratings is the maximum weight that tire can carry at a specified PSI. Normally an E rated truck tire at 80 psi is rated to carry 3042 pounds maximum. What does your door sticker say? Mine says 70 psi front and 65 psi rear (dually). Those tire pressures, in my truck's case, correspond to the air pressure needed for a maximum load. No use putting in more air if it isn't needed.

Go with your feelings, it won't increase what your truck is designed to carry. That is all, no other answer but you knew that.

Re-arching springs brings spring pack back to OEM state
Adding an extra leaf increases spring pack load capacity

Neither will increase the GVWR which is a MFG rating for CLASS of truck


Max Load Rating at MAX PSI is STAMPED on sidewall of tires

az dry heat. My door sticker says ~~GAWR FRT (3500lb) with265/70r16 32psi cold ~~ Rear (3760lb) 33psi.

Door sticker never saw my E rated tires

The tire rating is stamped right on the side of the tire. The tire manufacturer publishes a load inflation table. It will tell you how many PSI the tire needs to carry a certain weight. Get your axle weights using a truck scale, consult the chart, inflate accordingly.
How will reinforcing the springs add load carrying capacity? How could it not. Whenever a mechanical part is strengthened it gains better ability to do it's job. Swapping heavier duty springs, axles, tires, wheels, etc. onto a truck will in fact increase the ability of the truck to carry weight. It's just a machine and conforms to the laws of physics.
No, it won't change the sticker on the door. Lets say I have a 3500 truck with an 11,000 pound GVWR. My driver's door gets dented and I go to the junk yard and get a door from a 1500 truck to replace it. Now the door sticker's GVWR number is 7,500. I'm I know restricted to a GVWR of 7,500 with my 3500 truck because of what the sticker says?