I would say while the stack is out, if the radiator is in question rebuild like Eric did his with the larger dimple core style or replace with new wether factory or Davis aluminum. At 20 years old, It isn’t like its a bad idea anyways.
There was an upgrade condensor made that had better airflow and improved exchange rate, I don’t remember what year that upgrade was made. Either of the “Daves” would. The existing one is ok to run, not like a radiator that if fails from metal fatigue can destroy the new engine.
Charge air cooler? It isn’t like there is any examples of a hummer with one it hurt.
The oil and power steering both are fine unless you have a specific problem from damage. Unless you are going to go aluminum, then seriously consider the all aluminum package. Only draw back is the expense of it.
The last and certainly not least part is talk to Chris about coating all of it. Any new parts you have shipped to him first then from him to you. The use of the coatings on the stack is such an obvious one to me that it has never been a question of if I would do mine. Just affording to do it, kinda like the balanced flow waterpump on the 6.5 - not if but when.
While it is all out and new engine makes sense as to when.
Just need to question Chris about timing with the hurricane and all. I hope everyone in the Carolinas is holding in ok-
If the budget is tight , I get not doing it all new now for sure. And yes the cummins will run a more even temperature. But redoing at least the radiator would be at the top of my list.