The "50 MHz" means that it can run at up to 50 MHz. If you plug it into a socket fed by a 25 MHz clock, it'll run just fine - at 25 MHz. You would have to change the processor crystal oscillator and other stuff to make it go faster. Problem is that the bus and video timing are interconnected and have to stay at the old speed.
Sorry that I'm ignorant about 3000 hardware, so I can't be more specific on what else is required.
Like the man said, an upgrade is easier. So is a 600 MHz G3 - you could even fit the mobo in your case.
tony
