Just in case anyone will find this useful, as I was confused when I replaced the tank on my 1950 Plymouth last year. I ordered a replacement from MoparPro on eBay (free shipping). My original tank was out of the car when I got it but I had the old line and the extra-long fitting like diben shows. But I kept reading about this mysterious "ferrule" that I needed as well. I couldn't find it in my garage, I assumed it fell out when the previous owner removed the tank. I emailed MoparPro and asked if I needed the ferrule on the replacement tank and they said I did. But I couldn't get the new hard line threaded with the old fitting nor with the ferrule; there wasn't enough thread depth to catch on the new tank. I can't remember exactly what I did, but I think I bubble flared the line and used a regular brake line fitting from my pile 'o parts and it is working fine.
If you look at the old fitting, it looks like it almost has a bubble flare on the end. There seems to be some confusion about which years used the ferrule, it seems like 49+ did not use the ferrule and used the extra-long fitting.