You can't actually build a Mac clone. One of the core things that makes Apple computers different from your average PC is that they use something called EFI (Extensible Firmware Interface), and PC's use a BIOS. You can read up about the difference, and what makes EFI so much better than a legacy BIOS here. People have managed to flash Apple's EFI Firmware to motherboards that you can buy from a shop, but to do that, it requires tools which only Apple have.
However, you can still build an x86 computer and install a different version OS X 10.4 (OSx86) on it. This is basically a re-coded version of Apple's Tiger OS for x86 computers. If you would like to know what components are compatible with this, then there is a HCL (Hardware Compatibility List) available here: http://wiki.osx86project.org/wiki/index.php/HCL_10.4.8