Regarding spring rates... Well, I offer Tein's experience.
They list the Super Wagon damper as being compatible with the Galant EC5A (see link below) and that's rated at 5.0kg front and 3.0kg Rear.
http://www.tein.co.jp/e/price_list/swg_mitsubishi.html
The 'GT Wagon' is a more sports-focused setup (again, see below) but is listed for the Legnum only. This uses 8.0 and 5.0 F/R respectively.
Dan_G fitted Tein 'Super Wagon' dampers to his Legnum - read his thoughts here:
http://www.clubvr4.com/forum/showthr...ht=super+wagon
Tein also offer the 'Type CS' damper, according to their model lookup page for the EC5A, however, I can't find this in the details....
Here's Teins website if you want to search further:
http://www.tein.co.jp/e/price_list/index.html