This may be a stupid idea... There have been many methods discussed about squeezing a modern computer into an iMac G4. None have been 'perfect' and compromises have always been made. Space is the biggest problem. What if the imac's existing cooling system was kept intact? All we would need is to make a custom heatpipe that transfers heat from the new CPU (on a small motherboard) to the heatsink plates on the top part of the dome. As a rough guide, I've checked the thermal output on this page - a 2.66ghz core2duo system has the same BTU under load and a cooler BTU at idle as a G4 1.25ghz. So I reckon the existing cooling system could handle the new chip. Making a single part would be quite expensive. Maybe if there was enough interest, several could be produced to save money. After that, there is the issue of power supply, routing the ports and converting the video signal. All of that has already been done (I think the video conversion only worked with the newer imac G4 models).