I second the source Fan. I have a 2000Harney DP with the 3126B Cat and replaced my fan with the one from source Eng. They would not give me a guarantee as they were not sure that I would not have engine heating problems. Sine I put the fan on (about a 2 hour job) I have driven the coach over 1500 miles and not one problem. Extra power, a lot quieter and maybe better mileage. Not sure on that. I love it and kept the old one just in case I did have any problems.
They are great people and good to work with.
Busyguy