I need to replace a fluid leaking head gasket. Running Champion Alum heads. Compressions all look good. Someone said to use cometic 4.060 bore .040 , I thought 4.040 bore.040 would be the right size. Rookie looking for info. Should I use copper gasket sealer. Heads were installed 10 years ago, I haven't pulled the heads yet. Always want parts in hand first.