Swift Spring rates

[tmcmillan5]

Hi, I'm tying to get rid of some of the harshness in the rear of my 68 Chevelle convertible. I have Vari shock coilovers at all 4 corners 12" spring w 5.25" travel. 450 lbs fronts 200 lbs rear. I'm ok with the front of the car it's the rear end that I'd like to soften.

So my question is which spring rate. I'm going with Swift 12" progressive springs, my choice is either 150/400 lbs or 200/500 lbs. About a 3500 lbs car.



Any imput would be great. Thanks, Tony