Initially, that's probably the best way to go about it. I'm running my 3.5" TM leafs in the back. Without the trackbar the rear does flex pretty good. Not as much drop as the front but still decent. It's probably around
60/40.
Running buggy leafs, he'll have around 1.5" extra lift. If you look at the pict of
my Jeep, you'll get an idea of what it will look like. I went back to stock shackles and it sits level with my hard top on.
Cost wise... I bought the perches for $30 and bought some rear YJ leaf springs for $50 I think. It's really cheap if you're already lifted.