I use bios v12 on my Z68X-UD3H-B3My. I install with Quick start of Legacy mode.
Multibeast log:
11/20/15 09:31:51 - Starting MultiBeast 8.0.0-20151116
11/20/15 09:32:30 - Installing 'Bootloaders > Clover v2.3k r3320 Legacy Boot Mode'
11/20/15 09:32:42 - Installing 'BootVolume'
11/20/15 09:32:43 - Mounting EFI
11/20/15 09:32:43 - Installing 'Drivers > Misc > FakeSMC v6.18.1394'
11/20/15 09:33:04 - Installing 'Customize > System Definitions > Mac Pro > Mac Pro 3,1'
11/20/15 09:33:05 - Unmounting EFI
11/20/15 09:33:05 - Releasing XPC connection.
11/20/15 09:33:05 - Finished Installing.
Before installation, I cannot start without USB and with USB, the start freezes in the middle of starting.