All we have to do is get from that open pipe, through a muffler, and out the hole on the left of the photo. The muffler hangs from that bracket just to the left of center in this photo.
Instead of finding a muffler that exactly matches the original muffler, and reusing the existing pipes, we’ve found a muffler shop that will hang a muffler from the bracket, then bend some pipes to match.
It will be a simple solution to what seemed like a difficult problem and will only cost a couple hundred bucks. Whew!