Unfortunatly, it looks like our info was wiped out, so I'm writing up a synopsis. You can install a PCI IDE hard drive controller card, which will support another hard drive in your machine. This way you can have multiple drives. Though with the constraint inside the desktop unit, you may need to think of a different way of installing the drive. The floppy drive bay is the right width, though the height is an issue (and unfortunatly cannot verify). For $79-99 USD you can purchase a Sonnet PCI IDE ATA133 Controller card. Though the machine will not utilize theFULL read speed, it will speed up quite a bit. The only constrictions are processor speed, and the machines BUS.

It maybe easier, and more efficient for speed, to install a PCI IDE controller into the machine, ditching the original drive and just going with a huge drive that is on a card that can support awesome read/write speeds compared to the old drive. With the speed, you would not bog down the drive, because it will just be faster anyways. A 40gb ATA133 drive would just rock in that machine if you had the system folder on that drive as well.

And for ubergeek's comment:
Exactly ubergeek. The 8gb boot partition was only on Rev A-D iMacs and Beige G3's (Tower, Desktop, AIO). It was a pain, but there is a work around later on which involves merging partitions and having OS9 on the drive first. Such a damn pain in the butt. Though the 6360 does not have the right equipment, with ex post facto, the install can be done for OS X. Bravo again on your trial and error OS X install.
MacBook 2GHz Intel Core 2 Duo w/ 2GB DDR2 RAM & 120GB SATA 5400RPM HDD
Canon Rebel XTI
Google Cr-48 Beta Laptop