I used engine enamel and am pleased with it. That went over a chrome framed bmx. 8 months and it's still in great condition. I won't really ever worry about getting touchup mixed for a color that is dropped from a product lineup. I can get New Ford Gray all day long from several engine enamel manufacturers and a whole can is less than a small tube of touch up at the diy auto parts store. LOL, Ford isn't going away, but Chrysler & GM, as long as they keep getting bailouts I guess they'll be around. but seriously there are more paint colors for engine enamel today than there were 30 years ago or whatever. They've even got generic engine enamel colors.

http://www.duplicolor.com/products/enginePaint/