Does it boil over? 210 really isn't that hot if that's the max it hits. Many of the old GM cars turned the fan on at 108C which is 232F degrees I believe. Admittedly an engineering screwup but they wanted those engines to run hot for emissions.
Anyway, this might be an arguable oversimplification but if it doesn't get hot enough to loose coolant then you really don't have a heating problem. I agree that a 2 core might not be enough radiator.

5500 in third and a bog when you lock up? I am having a hard time visualizing why you even know that. What kind of driving situation encounters that in a 4x4?
Not hacking your tranny guy per se but you generally get what you pay for and if you bought a cheap tranny chances are good that you got one. The only 700R I drove much would overheat quite easily on a long pull when the converter was unlocked.