WTD: Long-tail cargo bike - complete or frame only...

Looking for a long-tail cargo bike, complete or frame only. Something like a Kona Ute or Minute, Surly Big Dummy, Yuba, Xtracycle etc.

Medium or large frame size and must have disc mounts front and rear. Frame must be ding and crack-free (paint chips are fine) but not fussed if components are a bit tired.

Location: will travel within the bottom half of the country for the right bike - as far north as Birmingham, or thereabouts.

Thanks.