Hi Hugh.

I leave about 1/2 inch from the top for expansion. DOT 3 will work fine as long as that's what's been used before. I suspect so. I think DOT 5 is synthetic and you are not supposed to mix the two of them.

Good luck. Post a few pics of you truck.

David.

David Gilmore
Stovebolt Pictures
Paint progress
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1950 Chevy 3600