I did not polish mine, but I glass beaded it and then coated it with Eastwoods Diamond Clear Coat. I have not run the engine yet, so I do not know how well this is going to hold up, but it is supposed to work for this type of application. Here's a link to some pic's of this engine:
261 Engine Pics


1954 GMC 1/2-ton Longbed
1971 Pontiac LeMans Sport