I'm not sure about the RAM, but if the CPUs have the same ZIF socket, then they should be compatible. Just set the lumpers on the AIO to whatever speed you want it to be, but try to have it right around 300MHz.
_________________
PPC Macs:

• Power Macintosh G4
  
• B&W Power Macintosh G4
  
• Power Macintosh 6500/225