coil over spring rate?

[Tiger]

Hi,
I'll get the Koni aluminum single adjustable coil overs for the front suspension on my 1968 small block chevelle.
As for the stroke I'll get whats closest to the C4 front shocks, but Jegs does not tell which lenght of spring to get (10" 12") for which shock.



And what spring rate should I use?? 500lbs/in, 600lbs/in, 700lbs/in???? I know its difficult to tell but a guess is appreciated.

same question for the rear C4 suspension, which spring rate is a good starting point ??

Thanks !
André