Coilover spring rate and lenght

I'd start with a 14/150

Can't help ya with anything solid but I'll pass along my thoughts. I hope they help...

I saw a few posts about this recently on another site and the "professional" recommendation seemed to be leaning toward using 12" springs rather than 14" springs. This was done specificly to improve on track performance by keeping the car hooked up after weight transfer happens during the launch, and the car is already off the line going down the track. After switching from a 14" to a 12" spring the cars were staying hooked up instead of unloading the rear tires around 300 ft when the front of the car is coming/settling back down.

As well, many folks chimed in and said they had been using the 12" springs on the street with an appropriate strut and were reporting no issues doing so. It was good discussion. However, it seemed that the combos being discussed had rear suspensions that were pretty well optimized, having been "blueprinted" and tweaked, and the front spring/strut choice was complimenting what had been in the rear as opposed to just being "picked".

With the power levels and tires you're working with, I'd contact a pro and tell them your goals, then let them make a solid recommendation based from their experience. It could be the difference between 1.6 60 ft's and 1.4's with your on track tune up. Based on your statement of, "The main thing is that the car hooks" I'm guessing a call to a pro would be a good choice so you're happy and don't wind up spending money twice...