Not to be a jerk, but I think this is pretty typical. Somebody has a few bucks in his pocket, finds an "old car" that needs "some work" and doesn't really stop to think that perhaps a car that cost a few more dollars at the get-go wouldn't need 12,000 dollars of parts and work. Take a 4,000 car, for example. You should be able to get a decent car with a driver paintjob that needs some odds and ends to the tune of a summer's work and a couple three grand worth of stuff. Boom, you've got 3 months and 6-7k in to a nice looking car. Whereas when you buy a car for a few hundred to 1500 bux, you can pretty much expect to have to go through the whole thing.
So here we are, you've got two cars in your yard that need an unknown amount of work, and now we know for a fact that one of them has serious structural issues. Don't kid yourself, a little patch-work welding and a ball-joint here or there is not what these cars need. You're talking about cars that are almost 40 years old. 40. Most houses need serious work after that long, let alone something that sits outside and gets moved all the time! Both of your cars need a frame-off and the one definitely needs to see a frame shop. I'm willing to bet if the huge x-member rusted through, you've got some frame issues (check the rear of the car where the frame meets the rear axle, betcha there's issues there). A little welding isn't going to make this car safe to drive, and its not fair to you, let alone the people on the road with you to have a car rolling around that hasn't had proper work done to it and been checked in a proper, thorough fashion. Now is the time to decide if you're in over your head and unload these cars.
K