I would not recommend trying to do this.
1.) It doesn't anonymize you any more than you already are (bitcoin is already anonymous and decentralized)
2.) Bitcoin client is essentially a torrent client. You are not supposed to run this on tor--it harms anonymity and puts undue stress on the network.
3.) Using tor browsing is safe enough--your goings on will not be tracked. If you're worried about it, use something like instawallet.
1.) A connected node could potentially identify the ip address that broadcast the transaction.
2.) Much lower bandwidth than a torrent... really not that much traffic.
3.) Instawallet is a good suggestion. If you want to run a native client on tor anyway, and you aren't on Windows, torify is your friend. If you run Windows, ask someone else.