The plastics from the older models wont fit.  The door from an older model will fit though as for my mod I used a G3 door/MB mount/pci slot cover.  I think I have an old G4 case or two and I know I have a spare MDD rear plastic if you want to give modding it a go.  You may end up hacking the rear, but that doesnt mean you cant fab up something to cover it.