I need a method to reinstall a SEP client package. Unfortunately, SEPM doesn't have a method in their GUI to do this...*nudgenudgewinkwink*, you must use the Migration and Deployment Wizard, and choose the default option Deploy the Client, and then Select and Existing Package to Deploy.
I found a clue in a thread at Symantec's forums where one can use the %PROGRAMFILES%\Symantec\Symantec Endpoint Protection Manager\tomcat\bin\ClientRemote.exe utility, which is usually only revealed when you use the wizard, or initially install the product.
You'll find your repository of packages you created in said installation at %PROGRAMFILES%\Symantec\Symantec Endpoint Protection Manager\Inetpub\ClientPackages, one folder for each package represented in SEPM, with a sub-folder called full. Unfortunately the folder names are named using the package checksum number, and I can't immediately tell by looking at the GUI which one is which. Fortunately for me, I only created two packages; a 32bit and 64bit version. If you look at the contents of the directory, it's pretty easy to determine which one is 32bit or 64bit. There will be a Symantec AntiVirus Win64.msi file in the 64bin version folder.
Simply choose the folder for your architecture, and push it to the client.