All you can do without pulling it is to test for play at the shifter and at the input and output shafts, both axial and radial... you'll need a special gauge for this. Also making sure it rotates in an all gears and inspect the transmission fluid.... Best bet is to tear it down though.
Just get the fasteners from Toyota, they're cheap enough.
If your power goals are under 350-400 (which with a W58 they better be) I'd just buy a stock clutch disc, get the flywheel resurfaced (an absolute MUST) or get a lightweight flywheel, and a higher pressure pressure plate from somewhere like HPF.
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