Most Airstreams use an LP rated copper tubing for the gas supply piping. Many MoHo's use black iron piping also, but that would add a lot of weight to an A/S. The connections are all flair fittings with double flairs at each end. Be careful that the copper tubing is rated for LP use and not the stuff that you would use in a water system. Make all of your bends smoothly with a tubing bender and be careful not to put any kinks in the lines. Pressurize the system with air when you are done as a test and check EVERY joint and connection with a 50/50 mix of Dawn and water as a bubble solution.
It's not very hard to do....just takes a little practice in getting those double flairs correct. Be careul not to over tighten those fittings also. Get them hand tight and then wrench them 1/3 of a turn, or 2 flats on the nut. They are easily distorted! And NO THREAD SEALANTS either