hey mate if i was you i will either get Coilover or the package from Sydneykid.
the reason is that the ride with just spring will change. It is accually becomes bad, and when driving above the limits
especially in a high preformance car you need handling and i know it is not track
Also most KIDS who have accidents and die on these road are because they have crap suspension.
Try Driving on the hume highway (bass hill) with just king springs........Trust me kidney Failure.