You could use 1/2 the total number of rivets as "guide pins" to locate the crown wheel,and use the closest fitting high tensile bolts & nuts to seat the crown wheel against the carrier face.Do half the rivets,remove the nuts & bolts and do the other half of the rivets.The 1st thing to do though,would be to run the carrier assembly between centers in a lathe,making sure the carrier bearing diameters are running true,then check the run-out of the crown wheel mounting face.If it's not running true,then take a light cut off the face so that when the crown wheel is mounted to the carrier,it will run true to its mounting face.