Keep in mind that trailer towing option on the Nitro has a special water pump mounted fan clutch and fan blade as part of of it (maybe you already have this with AC) , so maybe you need to address that also. I would add an addition electric fan as part of adding a trans cooler if affordable. Again Good Luck and check back and post your results to help others that may want to do the same project.
Water Pump With Fan Clutch
TYC 621690 Dodge Nitro Replacement Radiator/Condenser Cooling Fan Assembly
Nitro Year: 2007 (1 of 91,815 sold in 07)
Nitro Model: R/T 4X4 Stone White
CAT-BACK Exhaust, CAI, Projector Head Lamps
Fully-Equipped w/all factory options