This product is going to be your easiest and most economical option. It is exactly what I used to achieve the factory-paint look on my green Jet Flow...
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I suspect the paint-over-chrome on your Roadmaster tank was originally done the same or similar to the way Murray did theirs... A mask was applied to the areas that stay bright chrome, then the areas of chrome that were to have the candy paint topcoat were very lightly sandblasted. That gave the chrome a dull metallic aluminum look and a good base for the paint to adhere to.
Here's a couple of examples of the original paint-over-chrome technique on Murray products -
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Because the chrome on your Roadmaster tank is original and in good shape, it should already benefit from the original sandblasting/chrome-dulling process. Painting it to look original should be a matter of masking the areas that remain chrome, ensuring the surfaces to be painted are clean, then spray light, even coats of the Duplicolor Metalcast red until the desired shade and depth of color is achieved.
Carefully remove masking after paint is dry, then apply white pinstripes with One Shot enamel and your favorite pinstriping brush!
Good luck with your project!