generally speaking, this is not done on stock framed TJ's. It is more often seen on competition level rigs, with relocated suspension mounting points, tube frames/partial tube frame chassis, ect.
Coil overs have a number of advantages such as fully adjustable ride height, spring preload, spring # weight #, externally adjustable compression and rebound valving , ect, ect.
The average joe wouldnt know what to do with all these adjustments. It takes a fairly in depth knowledge of suspension to tune these to work properly/balanced.
[SIZE=2][COLOR=Navy]MK Motorsport & Fabrication