I've found a local manufacturer that will do custom springs for me for $120au, that's pretty cheap, but he wants the following information from me.
ride height (wheel arch to hub)
installed spring height
and then they want one of the springs to test it for stiffness, and will make the springs to suit whatever i want, stiffness and rideheight.
The height i basically want it where it is now, lots of rough roads around here and i do go off road a bit, so the bump travel and clearance will be appreciated, but stiffness i'm a little unsure about, I think about twice as stiff as the originals should be the go, but though i would get the opinion of someone who has fitted stiffer springs first...
I figure if i go to stiff i'm going to struggle to find dampers strong enough to cope?