PAC 1218 springs @ sdparts for $140 are great springs for FI! You'll even use you stock seals & ret. Easy swap!

 

thse two springs are the only ones i woud buy, unless different springs like the pac1218 come in a kit for a good price.

ls9 springs for $70. and these see boost in stock applications
GM LS9 Valve Springs Matched Sets - Lingenfelter Performance

or these brian tooley racing duals for $220
http://www.briantooleyracing.com/660...retainers.html