I'm using non-competition style Wagner brake pads on my C5 conversion front brakes using $6 parts store DOT-3 brake fluid and its just fine for daily driving. The main thing being that it is fresh and clean and well bled.
I found the old-style Autozone "conventional" coolant (inexpensive store branded coolant) to be recommended as well as a vintage jug of Prestone I had for some years waiting for an old car to come along.
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Trans oil: I have tried both the 10w-60 BMW Castrol and Amsoil 5w-30 synchomesh with good results. The BMW oil is easier to find.