I cleaned up the copper vacuum wiper tubing that came with the car when I bought it and firmly secured it to the backside of the dash to keep it from rattling. There must have been a lot of excess under there originally because now I have 5 1/2" sticking out from the firewall, on the engine side. How long should it be and should it stick straight out, perpendicular to the firewall, or bend down, parallel to the firewall? Thanks.
Since the wiper and tubing isn't original to a Model T, it can be what ever looks best to you.
The vacuum tubing for the original Ford/TRICO automatic wiper was black rubber. (NOS installation kits indicate that it was NOT the fabric-covered rubber tubing used on the 1928 Model A.) It is still made, and is available at any Pep Boys or other automotive shop. Rubber doesn't rattle, making it perfect for the Model T.