Uhh what is the point of this again? You're wanting to take a PowerPC system and add one of these SBCs in and run Windows on the side? This won't work well for a variety of reasons:
OS4 doesn't have Synergy, so you will need to use either a KVM or separate attachments to run this.
Power supplies in those systems aren't going to be able to provide necessary power requirements without upgrade, you're likely to blow a fuse in them or worse short out your system.
If you recall there was talk about adding a raspberry pi to Amigas, the consensus is you're putting a fast computer onto a slow computer in order to keep the old computer on life support.