I am currently getting parts together to rebuild the front end on my 69 fastback 302. I was thinking about going with a set of 1" lowering coils, but can't seem to find a place that sells the pair for the cars with small blocks (part# 5244). I have found many places that sell the big block pair (part# 5245). Are the coils for big blocks stiffer? What is the difference between them?