The problem with doing this is that the antennae for wifi and bluetooth are in the lid. you could buy something like this:

http://www.newegg.com/Product/Product.aspx?Item=N82E16823111011

If you want to get your hands dirty, so to speak, you could follow guides to remove the top case and once it is off find a way to mount the antennae, maybe you could fill in the are where the hinge is with some epoxy and put them in that. Here's a link to a take apart guide:

http://www.ifixit.com/Guide/Mac/PowerBook-G4-Al-17-Inch/55/