Do you mean new stanchions and bushes? Or fork bottoms too? Water sits in the bottom and its hard to inspect them. I'm not persuaded by hard chrome, I know its widely used but I currently have an A10 with std bare steel stanchions and they have cleaned up OK. I've run bikes with hard chrome stanchions (including a BSA) and once they pit they are done for, the hard chrome rips into the seals and bushes. Its fine if its kept with an oil film as on hydraulic cylinders but on forks it can stay damp.
Where is the corrosion?
Re springs, its both length and rate as you want to get the pre-load right so it settles at the correct ride height, then there's how firm it is which rather depends on how you ride.