There are formulas to find spring rate. But you need the cars actual weight, plus the front/rear weight ratio.
Also the spring rate will partly depend on HOW the coil over shocks are mounted. On a coil over/A-arm front suspension, how close to the front spindle the shock is installed/mounted on the bottom control arm effects spring rate. Closer to the spindle will reduce (some) the needed spring rate. Farther away needs more spring rate.
Same thing goes for the rear suspension. The farther away from the rear suspension's pivot point (I.C.) the coil over shock is mounted, (in front, over the top, or behind the housing) the less the required spring rate will be.
If you are looking for Koni's on epay, racejunk (etc) and want a "drag racing" valved Koni, be sure to ask if the shock has "SPA-1" on them. Road racing or dirt car valved shocks don't work well on a drag car.
460 street '66 Ranchero.......................finished someday.
460 race '70 Maverick..........................finished someday.
All 'glass Top Sportsman '69 Mustang......ummm, check back when I win big playing the Texas Lotto, or online poker.
page. Some ancient & newer local race video.
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