This is close, but it doesn't include the xmlns line, which appears to be needed for it to validate correctly. The XSLT I have below seems like it should do what I want, but it produces an error in the xsl:namespace declaration.

     <xsl:template match="ead">
         <xsl:element name="ead">
             <xsl:namespace name="">urn:isbn:1-931666-22-9</xsl:namespace>
             <xsl:attribute name="xsi:schemaLocation">urn:isbn:1-931666-22-9
                 http://www.loc.gov/ead/ead.xsd</xsl:attribute>
             <xsl:apply-templates/>
         </xsl:element>
     </xsl:template>
...
</xsl:stylesheet>

Michael Kay
Saxonica