I have had really good success with using duck carcasses for bait in Cage traps. In warm weather they go from being the ultimate cat bait to marginal possum bait in just a few days. I'm looking for suggestions on how to preserve them to possibly get a couple weeks out of them. I was thinking packing in salt might work?

I think that should work fine for you, or borax. I have some various birds, squirrel hides and rabbit faces I’ve done with borax and they’re still good after years in my fly tying box.