Welcome to the site. Where in Washington are you? Be nice to see a pic of your ride too!
Double flare. I have a 1950 3600 that I went through the same thing on. Get yourself a 4 ft 1/4 inch brake line and a cheap bending tool. That worked perfect to go from the master cylinder to the tee fitting along the pass side frame. Here's a pic.
brake line 1 brake line 2 Hope this helps.
PS, if you want to make your own, they are double flared fittings. Get yourself a good flaring tool.
