If you have not changed anything do you have an air bubble in the system from sitting? I never ran a fan shroud on my 40. Never had any overheating issues until the engine caught fire
But that's another story. 400hp stroked 383 by the way in SLC and Moab heat. Clutch fan, stock radiator, high volume water pump. Nothing fancy.
Don't get me wrong a should is a good thing. I just did not have the means at that time.