02-28-2017, 07:37 PM
If you have another older Mac that can boot 10.6.3, then you should be able to use it to install 10.6.3 onto the drive, then run the 10.6.8 combo update and then the MacPro should be able to boot from that drive.
You could do this by putting the MacPro into Target Disk Mode, and connecting it to another Mac via FireWire to do the install and update, then shut everything down and boot the MacPro.
You could do this by putting the MacPro into Target Disk Mode, and connecting it to another Mac via FireWire to do the install and update, then shut everything down and boot the MacPro.