My personal secret at getting the manifold shiney, or any alumimum part for that matter is take a brass cup wire wheel and put it on a 4 inch grinder and lightly hit all the surfaces. DO NOT do this on any gasket or seal surface. you can take some smaller rotary brushes and get the hard to reach spots. But on the LT1 intake if you do this by the time you get everything back on it will be shiney like new. Be advised this is somewaht dangerous so wear some protective gear like eye protection and heavy clothes. I usually wear welding gloves and a jacket when i do this. Learned this from a hotrodder that restored old parts and did not or could not have them blasted.