different kind of bastard leaf pack

I have a set of front and rear leafs from my YJ that were taken off for a 2-1/2" RE lift kit. I've not laid a tape measure to them to see what might or might not fit the existing XJ pack. Iis there any "rules of thumb" for me to follow or should they just go to the recycler?

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http://www.lunghd.com/Tech_Articles/Suspension_Steering_Axles_and_Brakes/Budget_Lift.htm

me and my housemate used two leaf springs out of a ford f150 and he got about 5-1/2" of lift out of it.