When you join a node with a different version of OneFS, that node will automatically be re-imaged to the same version as a cluster. This makes the join take about 10 minutes instead of 60 seconds, but does not cause any downtime.  There is no need to manually re-image the node to match the cluster. In the very old days < OneFS 5.5 I think, it was recommend to do this.
I need to do a Isilon Reimage to 6.5.4.1, but I cant find the Isilon software 6.5.4.1. Already check the page where are versions but not be the 6.5.4.1.   Someone could help me saying where to find it or have it upload it to an ftp.     
Isilon Reimage 6.5.4.1