Bah, Dont listen to those comments. I've done things because I wanted to know if they can be done! Yeah, sure, sometimes it ends up costing about the same for a brand new rifle, but lets do the math here.
The cheapest .223 rem semi rifle I know of is a mini-14. I've read some threads that they are no longer being imported, and a new one can easily cost you $1000. Used ones about $700.
The sks will cost you $200, which leaves you $500-$800 that you can use to 'convert' it to .223. I think, if its possible, you will be far under $600 when your done (not counting your time).
What better to start off with then a $200 rifle that you dont have a lot of money invested in. That way, if you screw up, your not out much.
Then, once you actually convert it to .223 rem, you have a 'one off' that you can hunt with down in S/W Ontario.
If you go ahead with your project, take LOTS of pics, and start a thread for us project junkies to follow along with! Now back to the ultimate question, what would one have to do if he wanted to change the sks to .223 rem? I know the sks can be rebarreled, but what would you have to do to the chamber/action/magazine to get the .223 rem in there?