Amusingly or depressingly depending on your viewpoint, the WinPE files haven't changed since 2008, so yes... until Altiris/Symantec actually supports WinPE 3 or 4 natively, use any set of WinPE files from 6.8 on, they're all the same, bit by bit.
I downloaded the FRM file and installer from the FTP site and that worked fine, with Linux and Freedos properly creating boot files. Server 2008 R2 is failing to create WinPE boot files for me through the PXE Configurator, but that appears to be a different issue... some undocumented change required to make Bootwiz actually run correctly through the network. Ah well.
The FTP links for DS 6.9 SP5 MR3 follow...
Main folder.
DS Installer.
FRM boot files.
Edit: Oh, and since I forgot to mention it, yes, MR3 does provide limited support for Windows 8 and Server 2012. It doesn't support remote installations or scripted installs, but won't choke up your whole server anymore.