Dave, there is a European company (Euroline I recall) who used to make brake line kits for the GT. They're already cut to length and flared correctly, but they still have to be bent to fit. Maybe GT Source can get these, or perhaps you can order them from Suselbeek (sp?) overseas, he took over the Parsget line of products, and I used to get my brake line kits from them. Alternatively, you can bend your own up, and cut and flare the lines to fit. You want to use 3/16" steel lines, with 10 mm x 1.00 pitch threads, and with an inverted flare. In fact I'm bending a set up this afternoon for the rear axle I'm rebuilding/modifying.
Bob