Something is wrong what you state about your Mac. A PM G4 350MHz can't operate on OS 10.5. OS 10.4.x is the max OS.
Click on the Apple at the top left of the Menu and click on About This Mac. What does it say about the OS X version and processor?
I'm using this cheap card.
I tested it and it works in my G4 and G5.
The seller is based in Brittain tough.
Get rid of the computer. A 350MHz G4 is completely useless for any kind of modern uses, even browsing the internet.
Look for any G5 model as a minimum, and Intel machine is the best choice. Even a $200 2006 MacBook will be several times faster than your G4.