BEARING ID 42MM, OD 75.8MM AND THICKNESS 39MM. WHICH BEARING I CAN USE THIS BEARING WILL BE USING FOR FAN PULLEY?

Here is a website that lets you put in the specifications of the bearign that you need and it will show you which to buy. from what I can tell, you will need one exactly like what you took out with the exact measurments. http://www.thefind.com/sports/browse-42mm-metric-ball-bearings