97 Suburban Water Pump Repair

I tried to remove the water pump on my 97 Suburban 1500 5.7 2WD. I had no trouble until trying to take the fan clutch off. I couldn't get it to come loose. I was able to remove the 4 bolts for the pulley. The fan clutch has a large nut 1 3/8 inch diameter. I have a wrench that fits it but I couldn't hold the pulley to loosen it. What is the trick to getting this thing off? Autozone, Checker rent a tool for Fords but not a GM truck.