there is no non disruptive option to migrate to cluster mode using only one array as the two controllers in the array need to be re-installed and re-initialized at the same time.
the only non disruptive way is with another array and only for FC clients. all other protocols will need some level of disruption. and the data have to be moved to a second array (it can be moved back to the first system afterward. but note that system is out of support at the end of this year anyway),
you can upgrade the OS to 8.2.5 7-mode non disruptively. and that version is supported until the platform end of support - and contain multiple bug and security fixes.