200 Avant springs

[e2e]

I need new springs in the rear of my 1990 200tq avant. I do NOT want to go
lower as I get to drive over real roads quite regularly. It seems that I
will have to get springs made as all aftermarket ones are lowered.
Q1:specs/dimensions of the stock springs please.
Q2:BTDT of getting springs made
Q3:spring rates, what is the stock rate (mine are now very soggy) and should
I get them made say 10% stiffer. If I get them made 10% stiffer do they then
need to be 10% shorter to maintain the standard ride height? Or is that the
whole point of lowered but stiffer aftermarket springs.
Q4:Just how far off the ground should my wheel arches be anyway(same as the
front?) 
-- 
Sam Clarkson