I would forget king springs all together, they are a rubbish quality spring, they have a high manufacturers fault rating, use Lovells - much higher grade, and u will find that suspension shops that know what they are doing will recommend them.
I spent $1200.00 on my suspension set up. I got a full set of clubby springs and had them reset to a my liking height. Purchased a fully adjustable camber kit(A MUST for 19" and above rims) to get even wear of the tyres, and had the front caster bushes re done, she handles amazing! Especially under braking, around round abouts, and general weaving in and out of lanes on the freeway, all in all responsiveness from the steering wheel is amazing.
I wanted to go lower in the front end, so i am getting shortened front shocks soon and then will reset the front springs again to avoid riding on bumpstops and killing the chasis, strut tower etc. Which will probably set me back another $800.00 or so
Go down to your local suspension specialist, i highly recommend the "Sunshine Suspension Centre" in Melbourne, award winning people for both service and products, probably australias leading independent suspension specialists. Speak to them, work out a budget, and get her sitting flush.
Just dont take short cuts i.e. Angle grinders, bags of cement, "Just put king springs bro you'll be fully sick", the suspension set up of a car is such a vital component of how your entire car behaves on the road, get it done right and you'll love your holden for ever.