The Eclipse dampers are from a second gen Mitsubishi Eclipse ('95-99 I believe). You'll need to stack some washers under the nut that bolts on the top plate because the threads do not go very far. you might have to swap the bearings in the top hats because the eclipse shaft diameter is 2mm thicker, Im not sure. The overall length of the damper is about 16mm shorter than the s13 damper with about 2mm more stroke.
As for the front housings, you can contact vielside180sx here:
http://www.nissanroadracing.com/showthread.php?t=1453
*I hope it's not a problem posting a link to another forum, but he's a wonderful person who makes a wonderful product and is well involved in the community.
The kit will come with everything you need to assemble the 8610 damper. After that, you'll just need some camber plates/strut mounts and some misc. washers/bearings. The price in parts should be close to the koni set up you posted in you first post. Don't be discouraged about the labor in piecing your own kit, it should be well worth it because it's built to your desires.
The DriftWork knuckles are wonderful products but a little pricey for the alleged drop in fit, especially for an s13. Besides that, a drop spindle is a wonderful way to lower your car without sacrificing performance.
You can use the front housing with the yellow set (I think you have too) but I'm not sure if you can with the 8610. I don't know the measurements off the top of my head to really conclude at the moment. You should check out nissanroadracing if you're really interested in the koni set up. Many drivers and pseudo engineers are over there that could give better first hand advice about the product.