I took a couple hours tonight, trimmed and tack-welded the puzzle pieces together on the tunnel piece that connects up to the firewall. It actually went pretty well with the TIG. I fit it close enough in most places to not need filler. There are a couple of gaps but nothing terrible. I trimmed the edges back a little more and it is starting to look OK. If I had a bead roller, I would roll a couple of beauty marks in it to make it look a little better.
I am taking next week off and plan to finish this and move on. See how that works out. It should weld in OK as long as I don’t get in a hurry and trim it wrong.