Thanks to Flowrider,
Macdctr and
splifingate I got it up and running on mine. Everything is working great except one thing:
After install I activated Filevault on my main drive like I always do on my machines. Encryption went fine, but the next time I rebooted it starts without the GUI login interface. Only terminal-text login. I have to type in username, choose to start computer and then password. This would not be a big hassle usually, but as I have and PC version of the GT 8800 graphics card in my Mac Pro 1,1 it does not show boot screen. I have to type it in blindly every time. So my question is really two questions:
1. How do I get back the GUI version of the login screen