No factory option LSD on the GS box. There were 3 different variants of the F5M42 box in the GS over the years, as far as I know, they are similar in make up to the boxes found in Cyborgs and 'Mivecs'. My suggestion would be to do your research to see if an LSD from a Colt box will fit, alternatively, just transplant the whole box.
cheers, the engine is actually in a colt and i have been using a cyborg box, diff is wrecked in it though so thought i might try the fto box as i reckon the ratios might be a bit better suited.