Idler Pullies....Which is Which??

[Electricat]

I'm just about to finish up my rod bearing and 60k work (finally!!) on my '95 ATX. I just went to put the two idler pullies on, and noticed that they are different. One is a simple stamped pulley, while the other has a heavier center piece. Which one of these goes in which position?? Just curious, anyone know why they are different??

Thanks!