Mustang GT Cooling Problem

1996 Ford Mustang GT , 4.6, 5 speed, 130,000 on body, 60,000 miles on engine. The issue is the car was running warmer than I think it should(never overheated but I don't want it to either). I have changed the thermostat, flushed the engine cooling system and replaced the anitfreeze with approved coolant. I have verified that the radiator has good flow. The car runs cooler (at idle is between the m and a in normal) but it still runs hotter than other Fords that I have owned. The question is should I replace the electric fan on the radiator or should I replace the radiator and fan. I have also been told that the cat converters could possibly be the issue. If you have any suggestions please let me know.

Thanks

possible causes:
clogged radiator internaly and externaly
worn out water pump
bad radiator cap
too high a concentration of coolant
is the fan coming on when it should and is there good air flow through the radiator?
engine timing
oil level