Dean, I did just change the manifold and muffler prior to the overheating problem.
I do live in northern Indiana but had used the tractor to plow snow with earlier in the week and it was fine.
Second time it overheated, it was sitting in the shop which is heated.
The radiator hoses appear fine but I do have new ones if needed.
I'm going to flush the system as suggested and wait for the new stat housing to come in.
Thanks for your help.