As backers' auditions go, "Gutenberg! The Musical!" " a wildly delusional conceit so full of itself that it boasts two exclamation points " doesn't stand a chance of making it to Broadway. That is, unless it can convince an audience of potential producers that it is witnessing the greatest creation since, well, the printing press. It greatly helps that this starry-eyed writer-composer duo from Nutley, New Jersey who …