I'm quite confident that the pressure plate for the GS-R has greater clamping force than the LS pressure plate. The stiffness of the pressure plate springs makes a big difference in how stiff or heavy a clutch feels.

If you're considering using a GSR clutch instead of a proper aftermarket clutch for your built LS, my advice would be to skip the GSR clutch altogether. The GSR clutch will not be as durable as a medium-duty aftermarket clutch & pressure plate.