In place with new fasteners. I like to use the Schnorr washers on top of flat washers so that the Schnorr washers do not embed themselves into the soft aluminum.
Note: I no longer use Schnorr washers in this situation. I've learned that they are not the best solution for this application. Instead, I use Moto Guzzi's thick wave washer that they specify for use on the newest models.
Photo courtesy of Gregory Bender.