AN-2s are dirt cheap. I wouldn't dismiss this deal as being for just the upgrades. I've heard of them going for $20k cash, as is/ where is (Poland).
One little problem is that the FAA won't certify them with a Normal or Utility airworthiness certificate. If you're lucky, you'll be able to get it certificated under Experimental/ Exhibition, which is essentially useless.
There are also the issues of parts availability, insurance, and that ripping 90kt cruise speed!