That brings up the factor I thought of when reading the post. Fitting the barrel should be nothing that a qualified smith or a machinist can't accomplish. Altering the magazine will be much harder. Look at the magazine box and follower of a M54 .30-30 and you will see what I mean. Just installing baffles fore and aft probably won't be enough.
Of course, a magazine isn't necessary unless you plan to hunt with it, and even then probably not. Were it mine, I would be sorely tempted to make it a single shot with maybe an aluminum feed tray built in place of a spring-fed magazine.
Lots to be said for a .30-30 bolt gun. It is an ideal platform (IMO) for experimentation, especially with cast bullets.
