I've never driven a GMT400 2500 Suburban, but do daily drive a GMT800 2500 suburban. I could not remember what leaf springs these have, but just looked and it's a 5 leaf pack. I can pack the wife and kids in there and may get a little better damping, so marginal better ride. I've towed a 4,500 trailer, same effect, but not at the same time thus yet.
I don't have complaints as far as ride quality; seems to ride "maybe" just a hair smoother than my 99 Silverado ECSB 1500 truck that I used for 12 years a daily driver, and that has 3 leaf pack. My other truck is a '00 GMT400 K3500 CCLB, and I can't really tell the difference on that one either (6 leaf pack), but the wheelbase is way different and a heavier truck altogether, LOL. My point is that it still rides like a truck, because that's what it is. Aside from putting new shocks, I would *cautiously* swap leafs to a 5 pack and go from there.
I know these trucks have different geometry as far as the rear axle, so you can't directly swap things without a lot of work. Also, SUV vs trucks and OBS vs NBS. So maybe really not useful information. You'd have to compare spring rates directly, which I don't know what they are. But just a comparison between other trucks may give some idea.
Another point is that the LT tires ride harsher than the P series tires. On my 99 Silverado I added a add-a-leaf deal to the back and it rode harsher. Adding a bags of sand to the bed made it ride better. That was on P series tires. Years later I removed the add-a-leaf, but changed to LT tires, and it seems to ride about the same...not sure if changing to P-series tires is worthwhile. I personally don't like P-series tires under load. They seem too soft. All of my trucks have Lts.
Looks like Rockauto shows leaf springs with 5, 6 and 8 packs, and it says it fits C/K1500 and 2500 Suburbans. I would call Husky Spring and maybe they can recommend something:
https://www.rockauto.com/en/catalog...n,7.4l+v8,1303715,suspension,leaf+spring,7544
There are 3 different widths, so I'm not sure how they make up for that? Maybe some sort of bushing?
Good luck.