Does anyone know of a good place to learn up on suspension stuff?

I am truing to figure out a good PPI or rebound rate for the coils, I was aiming around 400 because that is the softest the got for the ranger and I thing that still be street-able.

Another question is Shock valving, I have no idea what the numbers mean. I know one be for Compression and other for rebound but I dunno the rates and how it will effect handling,

I also took the measurements on my coils and compressed is around 11 3/4in while extended is around 13in, I plan on having around 4 inches of lift so if I am thinking correctly I would want coils that are going to be 17-18 extended length and 15-16 Collapsed right?

thanks!

HR