66 Dart GT HT Whatsitgonnabe?

You will need a tool that does whats called an inverted double flare. 45° automotive style. I practiced with mine for awhile on a short length of scrap tubing until i was able to get the double flare correct when i was rebuilding a 60 chevy el camino. Had to buy a 50 ft coil of brakeline tubing, and make all my own line for that car. The evenings of practice payed off. I had one leaker in the whole system. I cleaned it up a bit, and tightened it up. No leaks.