Well, I removed my dash tonight (there are a few rust holes high on the passenger firewall, and I didn't want welding to go on back there with the dash in). Before I even started, a couple pieces of the HVAC ductwork had fallen out from under the dash in pieces. While removing the dash, even being careful, a couple of the other sections essentially disintegrated. Extremely brittle. So, are these things available anywhere, or do I have to find used ones or fabricate something? A couple of them are completely unsalvagable - pieces less than an inch long.

Not sure if they are available from Nissan (doubtful) but someone with a parts car should be able to help you out for cheap.