This applies to Server 2012 and newer, but these directions are from when I moved VMs from a 2012 cluster to a 2012 R2 cluster.

1. On the new cluster, right-click on the cluster and choose More Actions -> Copy Cluster Roles
2. Choose the roles to copy, and then complete the wizard. This will set up the roles and their dependencies on the destination cluster.
3. Shut down the VMs on the source cluster
4. Take the relevant storage offline in Failover Cluster Manager (FCM)
5. Disconnect the iSCSI volumes on all source cluster nodes
6. Re-assign the LUNs to the new cluster nodes in your SAN of choice’s management console
7. Connect the LUNs on the destination cluster nodes, but leave the disks offline in disk management
8. In FCM, go to storage and bring the copied disks online. You should see the volume details reflected in the bottom details pane if all is successful.
9. Start the VMs