double flaring can be, well, a challenge. A quality flaring kit goes a loooong way to making them come out right, and the Autozone near me had some really cheap kits. It took some effort, but I was able to re-tube the entire 90 with it. The 88 I did back in the day and used the pre-fabbed lines. As long as you get the proper fittings, or can get adapters, it's pretty straight forward. Always get more length than you think you need, and always buy more lines than you need. You can always take them back.