the only reason you would change your fan from a puller to a pusher is if you install a turbo with an intake and you dont have enough room for the fan. then your going to have to install the fan on the opposite of the radiator and you MUST switch the leads. If dont reverse flow of the fan it will not blow cool air on the radiator. It depends on which side of the radiator you have the fan if it a pusher or puller. That is the ONLY reason you would switch the leads.