Here's a google photo I found of what it used to look like before I started hacking it up.
I guess it's a Thruster city cruiser (apparently Kent made them??) It seems pretty old, but the frame is made of good material at least. Welding on it is easy enough, so it's not just Chinese pot metal. I may need to reinforce some welds here and there (there's a big sticker above the bottom bracket that proudly proclaims that it's all tig welded). But the frame looks good enough to use!
I have a local person selling a giant rincon bike, and the wheels have disc front and rear. I'll have to see what condition it's in, but it's cheap and sounds promising.