Well, you're in .30-30 range, so like we were saying, wait until they step forward so you can put one behind the shoulder blade to try for the heart or double lung shot. Neck / head shot will certainly bring them down if you think your SKS is accurate enough.
For the sake of the animal, please be willing to pass up a less than perfect shot. This is a tough thing to do. Here's a good read on anatomy:
http://www.dundeesportsmansclub.com/...tplacement.pdf
Last thought - how's your tracking abilities?