From experience, the original Toyota are much better quality than normal aftermarket bolts. It's easy to tell when someone has replaced a Toyota bolt in the past, not only is the bolt head a different size, but it's usually rusty and is touch and go whether it comes out in one piece. I always re-use the original if possible, and have a supply of bolts that have come out of various celicas being broken / modified to use if needed. TCB tend to keep bolts for the same reason and you can usually get a bag of mixed bolts at a reasonable cost, or specific ones for special places.
I'm not certain whether brand new from Toyota nowadays are as good quality, the only ones I've tried are turbo nuts which were ok.
I also wouldn't go for stainless. Again from experience, these are very hard & sharp and tend to damage the threads they go in after a few times in & out.
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