I don't think the GS-R subframe is different from the RS or LS, but, I know the Type-R is reenforced to cope with a thicker rear sway bar. If you want to put a stiffer rear sway bar on an RS/LS (I think the GS-R as well), you need to reenforce the points under the bushings where the sway bar attaches so it doesn't end up tearing out.

That also brings up the point of the RS with a GS-R motor/transmission being superior to a real GS-R because it doesn't have a moonroof. I wouldn't be surprised if that's true since the Type-R has thicker stampings in the pilar and roof area. G3s are known to be squeeky; their chassis aren't very stiff.