I've used various uprated rear shock absorbers including Gaz & BGM, but for a road SIII, you can do yourself a favour by using a quality SII rear shock absorber as the effect to the front end geometry is to sharpen steering & the standard format silencer becomes less easy to ground out.
This was a common practice in the 70's when we managed to still wear through the box portion & would cut an inch strip out. All achieved on cr@p tyres of the time! Some of you just can't be trying, these days, especially with the much grippier tyres available
