I would pull the kick panel. You will be able to access and clean the drain holes. There is likely a lot of junk in there. Pulling the kick panel is a bit of a wrestling match.
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You won’t gain any access removing the fender.
There is also a drain hole at the base of the cowl panel if I remember right. It’s been a while since I built a first gen Camaro.
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You can access it from below without removing the fender. You should be able to use a long screwdriver etc to poke up in there and loosen the blockage while running some water into the cowl vent.
Don