Conversion should be no more difficult than any Lionel 3 to 2 rail job. A Weaver NE caboose would be easier and cheaper, and some are already 2 rail. If not, a quick change of trucks & couplers is easy. If you want interior lighting or working markers, you are probably already contemplating how to swing electrical pickups on the Lionel conversion. Just as easy to engineer on the Weaver. Lionel or Weaver, you still have to acquire 33" metal wheelsets in 2 rail. If I'm not mistaken, the last Weaver production even came with 2R lighting.
Bill Chaplik