This summer I added power brakes to '67 GTO. Bought new booster and dual Master for $125 or less, then measured the two steal lines so I knew how long the new lines need to be, note two different dia. Measured, bent, and put a long bend in the line as it goes into the master, then had my buddy put the old couple (that goes into the master from my old lines) on so we'd have the right size flair nut going into the master, did the same for the other line. You will need a vacuum port for the booster. I found that the 67 used a port in the rear of the q-jet. I do have the right/original port but opted to just get a barb fitting and 2' of line to get going for now!
Overall, this is a pretty easy fix if someone has a double flair (called something like that) brake line tool.