Anyone know thre difference between standard, heavy duty, and up country springs? I am thinking about changing the standard springs on 96 ZJ (V8 w/AC and 4WD). Dealer needs vin# or spring code to order springs. I have ZFM fronts and ZJT rears. How do I find codes of other springs that will fit my vwhicle?

Not sure of the difference for standard vs heavy duty. Maybe the difference between 4.0 and 5.2 motors and/or towing package.

Up Country was an upgraded spring that was about 1" taller than stock.

Are you looking for a lift? or just to replace sagging springs?