The rear spring rate will be a lot more critical than the front...
especially with drag racing. The same could almost be said
about valving....but the front and rear are both critical
for a proper launch. Just make sure your dampers (shocks) are properly set-up for drag racing..not street or roadracing.
I was getting ready to say that spring length won't matter squat
on a drag car...but then thought about it for a minute. If I'm wrong on this one...someone speak up. The front spring length
shouldn't be much of an issue...so use the 8 or 9 if you have a
short travel distance (save a little weight). Considering the
rear valving used...I would go for a little longer rear spring to prevent total compression of the spring during rear weight transfer. Then it all leads back to spring rate and compression