I would try for 433 or 466 since the bus speed is only 66mhz. i am not sure (cant remember) if you can reach 500 with the stock jumper block without OCing the bus to 83mhz in a Beige G3
that CPU made for being on a 100mhz bus so that should give you a little head room for OCing it.
putting any flavor of free OS is a PITA to get to run on a Beige G3. just to give you a little heads up, now OS X will instal and run fine (panther and tiger require you to use xpostfacto). i played around with ubuntu on my Yikes G4 and it was down right horrid, very slow and very unstable and hard to get things working properly altogether.