Ok,
There are multiple Airport cards.
1. Original- 802.11b, 12 Mbps, PCMCIA card, works with all G4 Macs except Firewire 800 MDD
2. Airport Extreme- 802.11b/g, 54 Mbps, Mini PCI card, works with G5 prior to late 2005, G4 firewire 800 MDD
3. Airport Extreme/Runway card- 802.11b/g, 54 Mbps, Runway card, works only with late 2005 dual core G5's.
4. Airport Express- 802.11a/b/g/n, 54/300 Mbps, Mini PCI-e card. Mac Pro and Intel Macs only.
The G4 AGP graphics uses the original Airport card ONLY!!! It can not use any Airport extreme card at all.
Original
http://www.welovemacs.com/ibkap.html
Airport Extreme
http://www.smalldog.com/product/12651640/atfgc
Runway card
http://www.amazon.com/gp/product/customer-images/B00081A2UO/ref=cmciu_pdp_images1/002-8945773-2392003?ie=UTF8&s=electronics&index=1#gallery
Airport express
http://www.thinksecret.com/news/0608airportexpress.html