The bumper guards aren't available after-market. It's E-Bay or nothing(most people don't like the BIG black rubber thing), but you can get earlier bumper guards to fit if you don't want to be "correct". I'm a Challenger guy, but from what I know the trunk chrome, might be do-able, but getting those "C" pieces are the TOUGH part.
If you need chrome racing mirrors for a 73, you can go two ways. Buy a crummy original set and get it re-chromed... or try your luck with the re-pro mirrors. I haven't heard alot of positives from the people that have gone re-pro, but that doesn't mean that it is bad( it's a new thing). There are only a few people that have tried it. I don't know your budget, but you should be able to get each side mirror re-chromed for $150, or so.
Mike