Thanks that's helpful to see the sticker. I'm trying to figure out if there's any relationship between the weights to reconstruct mine. My Gross is 4920 I believe. So something is different about yours at 5120.
There are 5 things weight-wise: The gross, the front gross, the back gross, and the reserve accessory weights (near bottom right, F0008 is front axle, T0149 is total reserve). I don't know what it means exactly. Somehow this all has to tie together but I have no idea how and I don't know why yours would be heavier (I've seen this on 97's too).
As to the springs the codes tell you what springs are in it and somewhere there must be a chart that tells the capacity of those springs so the gross weight difference could be due to that.
31" was stock tire for you as you know.
I have the decode for '97 in the shop manual but your sticker isn't even in the same format as mine and I'm pretty sure some codes are different so I won't confuse things by trying to decode it per '97 and it wouldn't really help you because you know what you have... except springs. Usually springs is two letters , I can't hazard a guess about yours. I don't think the "X" is DSO (dealer special order) or it'd be up on a different line.
Probably your truck is raised 2" oem to fit the 31" tires.
I thought, being the same gen, that your sticker/truck would be very similar to mine but turns out not so.
There are several guys on this forum who will know more about this and have access to more info that could help you. But my Oasis sheet doesn't say anything about springs (kind of odd).
I've been looking on my truck to see if I could find tags or stamped numbers on the springs but so far I don't find them.
I'm thinking that there are a variety of spring choices and that could well influence gross (and other) weights.
Sorry I can't help more but if you get a shop manual for your year it will tell you the spring codes. I do have a B for rear and W for front decoded but then the code should be WB not BW unless they reversed the order. I also have an X for rear, but why you have three letters in that box, I don't know, and I'd hesitate to use '97 decoding for it. Things are different, for instance I don't have code for your paint code. I have things on mine you don't have (different format) and I don't have the code for your tape striping.
Might be good to search out a set of shop manuals.