If you really intend to put an ATA (IDE) drive in your G5, we would like to direct you to a (in our opinion) better solution, proposed by Jefftrep, which was featured here about a year ago:
http://www.hardmac.com/niouzcontenu.php?date=2003-10-10#758
By replacing the IDE connector of the optical drive by a double one, it is possible to hook up and install an ATA drive above it.
