The only JIC suspensions I have seen come with their own spring dampers valved for the springs that come w/the suspension.
Ground Controls: If you call Ground Control and just buy their out of the box springs and adjusters for the DC2 ITR, then the springs will be heavy front and mild enough for the OEM shocks.
However, you could be opening up Pandora's box as far as suspension modifications go, and you might want to think this through quite thoroughly before you buy something.
If all you're after is lowering the car, then that's fine.
If you want to alter the way the car handles, then you should probably go ahead and spend a little more money up front.
The DC2 re-enforced ITR suspension can take very heavy springs, if you want, without harming the chassis.
A setup that has proved very popular among enthusiasts and part-time track people is the Ground Control setup with 400# Front and 500# Rear, together with Bilstein shocks. Many people have made that small change and been good with it for years.
KYB shocks are inexpensive and offer a surprising range of adjustability for the price.
Koni Yellow are a perennial favourite. You will not be able to go over 500# springs with the out of the box Koni Yellow valving, however.
If you want to know what I have, it's 500# Front, 750# Rear, and revalved Konis.