This sounds like a road that I have been down recently on a 40.  For the gaskets you can contact Olson's gaskets in Port Orchard Washington, they should have the patterns to make headgaskets and whatever you cant make by hand yourself, olsensgaskets.com and ph# 360-871-1207 

The piston rings can come from Otto Gas Engine Works, contact Dave Reed with bore size, ring groove width and depth at ph# 410-398-7340 or pistonrings.net

For the decals you can contact Lyle Dumont at oliverdecals.com or Dave Preuhs in Le Center Minnesota.  Dave has maintained one of the best web sites for Hart Parrs at <!-- w --><a class="postlink" href="http://www.geocities.com/hartparrtractors/">www.geocities.com/hartparrtractors/</a><!-- w -->