You want to move data on local drives to a LUN on an array ? AFAIK (and I've done this before), you can simply do this with "Ghost". Make sure the HBA is configured to boot from a LUN (if the hosts needs to "boot from SAN" as well) and that the HBA is the boot controller (if the hosts needs to "boot from SAN").
OR is meant for migration purposes, so for example when you want to move data from one array to another.

Open Replicator requires you to be able to map storage between storage initiators so local storage on a host is not going to be a possibility for either an OR source or target device.

In the past (I'm not an Exchange admin so the terms may be incorrect) I've seen migrations done by moving the Exchange stores and also individual mailboxes which can reduce downtime (though increase manual effort) with a side result being that you can optimize your internal Exchange layout a bit.

I'm a little confused though - if you are running an Exchange cluster you must be using something other than true internal drives for multiple hosts to be sharing them in a cluster setup?

I was thinking the same thing. A "cluster in a box" ? Shared storage like that Compaq Proliant 1850 a while ago had ? Or some low end MSA or something ?

Yes, a cluster in a box. Our current MSA storage is getting beat up. This is causing significant slow downs. We want to move all current MSA drives to out EMC SYM. Also, this will allow us to use e-mail eXtender for backups. Are there any sugestions to moving the data with Open Migrator?

Open Migrator is a tool used for host based migrations. I dont think you need to use Open Migrator/Open replicator for migration from local disk to SAN attached Storage. You can use Ghost as suggested by RRR. It is easy to use and an effective one.