Realize you already solved your problem, but can tell you that from my personal experience with chrome spray paint, it is NOT a mirror-like finish; it tends to look more like slightly-hazy polished aluminum. Plus, you'd have a bear of a time blending it in to any existing genuine chrome.
Might be why they decided to paint the whole car! They kept trying to blend and blend until they ran out of original paint! [
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Hope your hubcaps work well. Knowing trailers can bounce around a lot, just make sure you always keep an eye on 'em in case they pop off after a pothole!
Good luck! [^]