Lots of options, let's see if we can find any that make sense:
Thread the barrel for chokes: Not too hard to do, but you'll still have a 20" barrel with a long magazine. Fine for turkeys, oddly balanced for any sort of wingshooting.
Swap for a 6 shot mag / 28" barrel: Possible, you'll need a strap wrench to unscrew the magazine tube. You'll need a short mag and a longer barrel, but you should have no problem finding someone who wants the old parts.
Personally, I think I'd just sell the Cruiser as is and buy a 500 set up for hunting.