JjS - What Tony said. You can go to the tech section on my website to see how I've used the neutral line concept. Several of the books mentioned in the Where to Start Reading thread will help with all the calcs. The B-body axles may slightly change the track and therefore the motion ratio.

I actually find rear leafs more problematic because its hard to get good specific info from many of the vendors. There's quite a bit to leaf spring design. Besides rate, there is arch, numbers and thickness of leaves (especially main leaf), interleaf, leaf end shape and placement, front to rear spring ratio, and eye placement. If you want to discuss more about rear leafs or more about your own set up its probably best to start a new thread.