I'm gonna swing by the metal shop tomorrow and just see what they have to say about working with it, but it's a good 2-3 feet of rot from about the back axle on up. The gap between the bottom of the frame and the top is about an inch. My gut feeling is that there isn't much good material left to patch, so I doubt I go that route.
As for getting a new frame... I'm not sure I'm up to the task. I'm sure I could learn, but I have such little experience with cars. This truck was my first attempt at teaching myself (please read "spent hours reading on here and finally mustering the guts to try the easy things"). I suppose I could use it as a bigger learning experience, but it seems like quite the under taking for someone with as little experience as I have.
If I'm gonna sell it, I will sell it probably as a parts truck, but at the most with full disclosure of everything wrong with it. Anyone buying a T4R deserves to know what they're getting!