Elvis Costello is responsible for some 600 published songs, but that’s hardly kept him from exploring the catalogs of fellow artists. Below, in no particular order, we’re taking a look at 20 of the best covers Costello has either recorded officially or performed live. And to be extra clear: this merely scratches the surface. This writer, for example, has witnessed Costello perform covers of things such as “Like a Rolling Stone” by Bob Dylan and “Domino” by Van Morrison, neither of which appear to have found their way to YouTube yet. But in the meantime, here are 20 excellent interpretations, E…