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Well as you mentioned they don't have anything in the ratio's anyway, but on top of that those are only 7.5" gear sets. 7.5" is for Toyota Tacoma's, 4runners, and MKII Celica-Supra's..
MKIII, MKIV, GS300/400/430 all have 8" gears and the Turbo 6spd MKIV's have bigger 8.7" gears.
You can swap a whole 8.7" 6-spd MKIV pumpkin which has 3.13's into a GS as long as you get the axleshafts with it. That would get you a slightly longer gear, but probably not enough to be worth hassling with unless you were doing it to gain the LSD as well.