I wouldn't think they are worth much TBH, but you never know! Try selling it and find out, best place is the inevitable eBay....
If I had gone to the trouble of stripping a landy down to replace the chassis, I would never buy a secondhand one regardless as it seems kind of pointless. However, if someone's desperate to get their motor rebuilt and cannot afford a new one I suppose it would make sense.
Good luck anyway!