Seriously, find a good suspension shop. If you need different springs all depends on your weight, how much (weight) do you plan on carrying, are you going off-road or staying on-road. There are lots of good videos showing you how to set up basic preload.
Depending on how much different the springs are you may need revalving of the forks and shock as well.
Depending on how much different the springs are you may need revalving of the forks and shock as well.