I have been told at one time you could send your #4 to Longbranch and they would convert it of $39 or some ridiculous price like that. Thousands were converted. There were even a few on the E&E board just recently.
These days making a #4 into a target rifle is like making a silk purse from a pigs ear. There a plenty of better actions around to base a target rifle on, with alot less work then modifying a #4.
If you are looking for an entry level target rifle, you would be better off with a Savage or Remington models in a laminated stock. Have a bottom rail and target sights installed. Ready to roll for about $1500.
Or you go the route of the #4 you will need a barrel $400-$600 intalled, action squared up, new extractor fitted, one piece stock with all the goodies and a good set of sights. It won't take long to get over $1500