I was planning to install the Sonic .85 springs and Katana rear shock on my daily commuter GS500F, but I decided to change bikes. I paid $80 for the Sonic springs and $50 for the Katana shock (eBay). I'll sell it all to someone for $75+shipping. The Sonic springs are still in the packaging from Sonic (with instructions) and the Katana shock looks to be in good condition. I'll sell separately too if you are interested.
The suspension parts are SOLD - Thanks for looking.