That's odd, my front end sunk maybe a 1/2 inch, but I have aftermarket coils. I think it's only like 100-150lbs more than the 2.5.
You're not going to find much in the way of JY springs that will lift you more than ZJ V8 springs. I do remember something about F150 coils springs. DO a search on Google "Jeep f150 coils", that should get you some info.
98 TJ 5.9 Stretched and big axles
01 F250 Powerstroke 7.3/ZF6