idk, we have 2 closed system jeeps and 3 open system jeeps, (cherokee's and manche's) all 4.0Ls and the two closed system jeeps have ALWAYS run cooler than the open system jeeps.
not to mention how god awful it is to get an open system to drink coolant through the rad-cap.
i see no difference between the two that warrants spending any money to upgrade, if we lived in the desert and were overheating constantly i could see upgrading all the stuff and trying to make her run as cool as possible to prevent disaster, but that's not the case
from what i've seen just maintain what you've got and you'll have no problems.
and ALMOST EVERY 4.0L will need a replacement radiator at some point. its just life.