Basically, you're painting over chrome or polished stainless. I painted a set of rallys I had on my '70 LeSabre with Martin-Signor semi-gloss black from NAPA. I had one NOS rim that was semi gloss in the painted sections and three others with nice chrome and ugly paint. Masking it off was a pain, but the results were worth it. If the '63 has narrow painted areas, visit a drafting supply store and ask for "Chart-Pak." It's vinyl tape in very consistent widths. Pin stripe tape might work as well. Pick up an X-Acto knife and a supply of #11 blades and change them often. Mask everything else with plain masking tape and paint away. I scuff sanded with 400 grit, then washed away the dust before masking. Practice painting before doing the hubcaps. I always get an extra can.