4 banger springs have a softer spring rate and are great for drag racing. The weight of the v8 compresses the springs so it sits lower. Now i was told it only works with used springs due to being worn but i have never tried new ones.
I run frpp springs (its been a while, I dont recall if its b or c) with the previously used isolators, and Monroe shocks/struts. Was all I could afford at the time, heh. But it rides pretty nice, and it handles great.