Vintage Air Gen IV with stock defrost ducting ?

[scherp69]

When I was doing some welding on my firewall, I ended up having a bit of a fire underneath the dash Unfortunately my stock defrost ducting ended up getting melted and is no longer useable. I have a line on another one for a smoking deal and don't want the guy to have to wait long for my decision. Today I ordered a Vintage Air Gen IV set up and am wondering if I need to replace the stock defrost ducting or if it even gets used, or if the kits usually come with new ducting. Any info would be great. Thanks in advance.