I bought a pair of LS front calipers, and the guy ended up sending me the rears as well. Since I have them, will these bolt up to the rear knuckle on my 2GS? And if so, will there be any braking performance gain over the stock 2GS rear calipers?

 

Try them on and find out? I've heard of LS430 calipers being used. I'm sure either way the difference is negligible on a car like the GS- good pads and tires would make much more of a difference.