As Edward said, you need to pull the c-clip out first. This will allow you to pull the hard line through the frame. Once through the frame you can put a wrench on the rubber line and flarenut wrench on the hard line. If you don't pull the c-clip it's difficult to get the flare nut wrench on...
Here's a pic of a near original 84 Scottsdale I picked up last week. At this point I'll probably have more questions than answers, but hopefully I can contribute as I learn more about this truck