What kind of CPU's will work in my GigE Powermac?

I have a single 400MHz GigE PowerMac, will I be able to put an Apple OEM Dual 450/500 daughtercard from another GigE PM in there?

Any other CPU's besides the Sonnet/Powerlogix/etc. upgrades?

Am I correct in assuming a Quicksilver processor would not work since it has the 133MHz BUS?