spring rate clculator??

[69chevydr]

Is there a website that I can see what rate rear spring I need for my GEN1 with a 10" over swingarm? Or whom I can talk to ? I had a 6" over arm and had a 850lb spring need to see if I need a higher rate. Thanks

 

[BiggDaddyBusa08]

Try racetech.com There are some other companies to chechout but I dont remember them right now,but Im sure some1 will post up some other sites.