Bilsteins are nice and stiff. Also look into Old man emu. Someone mentioned those on here, and they are great shocks I know forst hand, but Im not sure if they make shocks for H3's although anything will work as long as its the right weight rating, length and stiffness you want. Adjustable Kings might be an option too, no coils.
I also suggested to Bebes replacing stock leafs with Deavers, but kind of expensive.
http://www.deaverspring.com/products.htm