Hi TakingARide,
all sorts of questions here.
Before you spend any money on the project, can you register it in your name?
Assuming yes, is the cost of that pile'o'parts low enough to justify it's purchase vs buying a runner?
Do you have the welding gear and the skills to put that frame back together?
At a pure guess, I'd expect a welder would want at least a C-note to weld the thing back together and that's if you did all the prep-work.
If it can be reassembled, welding is welding and you may as well keep the rear suspension as not.