After some research I discovered that GM A-Body cars (such as Buick Sportwagon, Chevy Chevelle etc) have front suspension designed for safety (read understeer). So as the suspension moves up positive camber is created. So it would not be ideal to lower the front end with springs. So the best option is drop spindles so the geometry isn't affected.
I got some 2" drop spindles from USA. Were about a quarter the price of the same on Trade Me. Thanks to Dad for getting these and Kelly for bringing them back in your lugguge.
Here you can see the difference between a stock spindle and the drop spindle.
Before and after
So at the moment we've got some 70's rake going on. The plan now is to get some springs made for the rear to drop it 3" and cut half a coil from the front springs to lower another 1". It has air shocks in the back, which is handy, but the plastic pipe is split and leaking so I'll need to find some more pipe somewhere.