I had the same problem when I did mine. Nothing would work...I tried a 600lb impact wrench, tried the bump starter method, tried putting the truck in gear to hold the pulley but it didnt hold the pulley well enough. What worked for me and will work for you is take a good sized chain wrench and wrap it around the pulley (be sure to wrap a towel around the pulley first so the chain wrench doesnt chew up the pulley. Get the chain wrench tight and rest the handle under the drivers side frame rail. Then get a breaker bar and 4ft or bigger piece of steel pipe and give it a rip. The harder you pull on the pipe the tighter the chain wrench gets and will hold that pulley in place.