Hi,
   Are you sure the thermostat is installed right side up? It will not open properly. I found one of my old tractors with it installed upside down... don't know who did it, t'was before me, so it always ran hot too. I would also check to see that the waterpump is working properly. I also found an old chevy which had the wrong gasket and closed off part of the water passage.
 Just a few things to check.
             Cal