The wrangler should be a coil spring setup, not leaf springs. You would need to source or make some longer springs and likely lengthen all the control arms. Check out my tjeepster build thread. I custom built a long arm coil spring setup on that one. I am not familiar with the Tamiya kit so you may get away with spacers if you only need a tiny lift?
http://www.modelcarsmag.com/forums/topic/150899-tjeepster/page/3/