Need to cool off a little

I have a 2000 Sport with the 4.0L in-line 6 cylinder engine and the AW4 transmission. I bought it new and opted for the 2WD because I like the looks and ruggedness of my second Jeep Cherokee (my first was a well-worn '94) , but do not necessarily need 4WD driving in LA and Orange County California traffic as is my routine. I would like to help the 69,000 mile engine run cooler in this stop and go traffic and summer is approaching. Does anyone out there know where I can get a heavier duty radiator that will bolt in without modifications, be California legal and not negatively affect the Cat converter, smog devices, ect by allowing the engine to run cooler?
It gets up to 220 degrees on a hot day sitting in traffic and although it doesn't overheat, I would just like it to run a little cooler for my own peace of mind as the engine ages.
tb