How much extra weight are you carrying in the back? The Icon/OME combo may net considerably more than 2.5" of lift if you don't have some significant extra weight bolted on. From the pictures it looks like a stock bumper & hitch w/ a swing out, any plans for additional weight back there?
The Icon rears are charged to 250psi, which will give you an extra 3/4 to 1" lift on their own. On my 96, the Icon/890 rear combo netted a solid 3.5" of lift compared to factory 99 springs (24.5" hub center to fender, 99 coils are 21" according to the interwebs). This would mean more like 4.5" compared to your 98, when I first bolted them on I saw over 5" of lift before the coils settled. It rode very firm and even with almost 400lbs of concrete it sat a tad high in the back compared to the 2" icon lift in front IIRC. These numbers were with a CBI hybrid rear bumper, which weighs about 40lbs more than the factory bumper & hitch combo but no additional weight over stock.
My original plan was a set of OME 906 coils but their short uncompressed length meant they could easily fall out with the rear shocks at full extension. The Icon shocks allow more droop than the factory or OME shocks.
I have since gone back to a factory rear bumper & hitch (the CBI doesn't fit a factory spare, stupid) and fresh '99 OEM coils. The result is perfect for me. I will have to re-measure but the rear sat level to 0.5" lower than the front icons with this combo (left at 2" lift as set up by Icon). I'm adjusting the fronts down to sit slightly lower, but I prefer less lift. The ride is perfect, controlled, but never harsh. I did a road trip last summer w/ 5 people, a full load of gear & a full roof top box (it was cozy) and it handled the load no problem. Definitely sagged a chunk in the rear with that much weight, but was still controlled and never bottomed out.
For reference, here's a photo of the Icon/OME 890/CBI bumper combo w/ 265 Duratracs. It's an awkward angle but all I can find right now.
