the king springs will make a difference to the handling, wait till the car is ready to drive before buying tyres/springs ect. that way you can set it up according to the weight of the vehicle. you will be able to get the right rate spring 4 the application. As for putting lowering blocks in the back, why would you ruin all the effort you put into the conversion and setting up the front end by putting lowering blocks in the back end? Having a high powered motor churning out 140 odd kw stock into a rear end lowered with lowering blocks is lethal. you see, the blocks allow extra movement and cause the rear end to squirm around under hard acceleration and can end up having the diff facing a direction other than straight, causing the rear end to track sideways. Not nice. Specially when youve spent so much time and effort building a sweet ride! Fork out the extra couple of bucks and get the rear springs done properly.You wont regret it.