The other option which I did do, is put an Isuzzu Impulse rear end under my GT, which is 4 " wider that the stock GT. Plus you get 3.90 gears and rear disc brakes. Now I am working on a front suspension to get the same track width as the rear, which will have coil springs instead of the transverse spring as the GT. Now one can put the Kadett 'C' front suspension under a GT with only minor modifications which will 3/4" wider than the GT front suspension, also am considering the Impulse front suspension which can provide power steering for the GT.
This is definetly safer than spacers. But again it is just a thought.