MaysEffect

The rear doesn't really matter as far as fitment goes unless you have a true coilover setup (oem is divorced spring mount). The front needs to match length and spring I.D to the O.D of the strut to fit. If the length of the spring doesn't properly match then your preloads will be considerably off and this will ultimately change how the damper and spring work together.

So no you shouldn't. You are best off getting everything properly fitted up first before picking springs and determining the potential ride height you want and getting the proper springs to match that ride height. Of course you can try fitting everything up with current springs and see how it works out as you go, the car will most likely be around the same height as before, all things being equal. If it isn't up to your standards you can try again with something else.

As far as damper valving is concerned, you may not need to change this as long as the total spring load is relatively the same for what you have and what it was tuned for. In essence, at a given height the total load on the spring should be close to the same for one spring versus another. You won't know this info unless you bench test the springs.

When installing the dampers make sure they are set at full soft for both rebound and compression (bump) if they are separate.

When adjusting the damper stiffer, if you happen to notice that the ride only gets harsher but still bottoms out or rolls too much, your springs may be too soft or you don't have enough preload.

If your spring preload is already adjusted past 1 inch and the car is still too low or compressing too much, your springs are too soft.

Finding out if the damper is too stiff or too soft is a fairly difficult analysis under normal conditions. Because the dampers have adjustable bypass rates that are capable of matching a plethora of spring rates, they'd need to be considerably too stiff or too soft to notice it not being acceptable for your car. Unless you change the weight of the vehicle considerably, you'd probably be fine with how it is currently setup. Also, unless the dampers are damaged or void of nitrogen pressure. Then you shouldn't have to change the valving.

If you have to set the dampers over 75% stiff no matter what and they start to get soft quickly. Then they are probably too soft.

If they are too stiff even before 50% stiffness and only seem to get harder over time, the valving is probably too stiff.

The optimal damper setting should be around 40-60% adjustment. If for any reason it only works at either full soft or full stiff, then it is not setup right for your needs, or damaged.