I laid a pair of JKU Rubicon springs next to a set of Rubicon express 5.5 inch springs. The inside diameter is the same as the JK spring. JK fronts springs fit TJ. TJ springs fit XJ. How much lift you get who knows.
If you look at the polyperformance.com site for jeep coils. It shows you the advertised height of their springs for JK, TJ, XJ etc. For example, IIRC, JK 2" springs would be a stock height XJ spring, although probably different spring rate.