I picked up some one inch diameter flex hose in order to do some duct re-routing in my K.I.T.T. for the new Knight Rider 2 TV dash. Oddly enough Canadian Tire sells the one inch flex tubing but none of the accessories like couplers or dash vents so I had to get a little creative with some plumbing pieces and a piece of plastic from an old broken DVD player's casing.
I Had to cut a square 4 3/4" in diameter and cut a hole in the middle big enough to screw in the plumbing pipe elbow that I would attach my flex hose onto using a Zip Tie. I screwed the plastic cover I made onto the original OEM dash with some automotive screws, the kind with the washer already attached at the head of the screw. I thought that perhaps I might need to add some thin high density foam rubber onto the back of my mounting plate but as it turned out the fit was more than good enough to not need to. You can if you find your fit is not flush with the dash, but in my case it was a perfect fit so it will re direct the air flow really well into the flex hose that I will re-route to a coupler I will attach to after market dash vents I can pick up from Classics Auto.
Below is a couple of pictures of the plumbing parts I picked up and my custom mounting plate I made from plastic from a broken DVD player's casing.