Disconnected the battery and antenna cables. Turned the panel and bulkhead assembly 180 degrees so I would have good access to the bulkhead panel. Completed termination of CAN bus. Drilled 1" hole for GMC cable in bulkhead using step drill. To get the connector to fit through the hole the grommet and shell of the connector must be removed. Now I understand why they offer a tray for the GMC 507 and wish I had opted for that solution.