Why not just use Disk Utility?
You can install OS X on the same drive without losing OS 9. You can do it in as little as 1GB of space. Then use Monolingual afterwards to remove all the language translations of the OS that you won't be using.
My suggestion would be though to install OS X on a separate partition. Trim out as much cruft from the OS 9 install as you can (ie any leftover personal documents from the previous owner, stuff like that), write down how much space it uses, then image it elsewhere. Reformat the internal HD into two partitions, leaving enough room for OS 9 in the second one. Install OS X on the first partition, then restore OS 9 to the second one.
That way if either partition or OS gets corrupted, you still have the other one to boot from to attempt a repair and rescue.
Epic score by the way
