That had a bushing in the tail wheel. Parts are going to be limited to ones off of used machines. You can get most of the wear parts for the bottoms. Try the Floyd County Museum to see if they have a copy of the manual for that plow. You can find contact info for them at <!-- w --><a class="postlink" href="http://www.olivertractormanuals.org">www.olivertractormanuals.org</a><!-- w --> 
The owners manuals back then commonly included setup and parts information, so if you can get one, it would be a big help.