DR - Moving databases from Active/Active cluster to Standalone server with LUN sync
I'd stay away from the scripting and detach/attach methods. I've done two migrations in the past nine months and was convinced that a better method would be to backup and restore the databases. That way you have a last-known good configuration point-in-time restore.

So here's my thought process. 


Restart the source instance in single-user mode
Backup your databases WITH COPY_ONLY, COMPRESSION
Stop the old instance. Take it offline. Pull the network cables, if you must.
Restart the new instance in single-user mode
Restore master
Change the location of tempdb (see below)
Restore model and msdb
Restart the instance. 
Restore your user databases.


Please note that you will need to do some cleanup on the instance names since you're moving from what I assume will be a named instance from your Multi-Instance Cluster to what I assume will be the default instance on a dedicated piece of hardware.

I may have misunderstood what you meant by "replicated." Do you mean that you're going to provision LUNs of the same size (you've already mentioned letters) on your SAN that you attach to new hardware? In this case, you're not describing a DR scenario at all. You're simply describing the provisioning of hardware for your new SQL instance. Disaster recovery would be how you plan to recover from the failure of these instances.

Naturally you know that you're moving away from a High Availability solution. I hope you're not relying on your SAN to do both HA and DR.