Yes, it will work, but not without some modifications. It will not run at the rated speed because of the slower bus speed. You will need to adjust it to run nearest to the correct speed. I dont recall if you need a 12v added for that one or not (someone will chime in on that). I also think you need to remove one of the ata connectors too. Is it worth it? Probably not unless the cpu is free. Also, make sure it has the cache chips on it, if it doesn't its a turd from the quick silver.
I went straight from the Smurf to an MDD, so never really did much playing with the older G4s. There is much less scope for the Cube due to power and space restrictions. Currently building a RAID box out of a DA board and 733MHz chip but a dual 1GHz Quicksilver just blew its board at work so the chip might be going begging.....
I know this is a bit off-topic and not what you wanted to do (not to mention the thread being a year old <_< >_> ) but for the sake of people using the search function(I know, rare.. but still), a Sawtooth CPU can be dropped into a Digital Audio motherboard with no changes to the multi. ASP might lie to you and say it is faster than it actually is but after benching it the CPU's speed is verified.
Now, I know that most of you would never actually want to do this. I am only pointing this out for emergencies when your DA CPU has failed or you are testing a board or a DA CPU is not available or something.
Speeds from 350-500Mhz benched below(click to enlarge if you have trouble seeing) http://thar.us/view/1936 The only thing that changed between tests was the CPU's multi. The G3 listed was the scores that came with the app.