Servo pulley striped

Hey my all-knowing US screwdriver. The following problem with the 84 Trans Am. belt disc is a bit oblique and stripes the iron behind where the servo pump is in it. Photo in the appendix! Furthermore, the disc is a bit loosely speaking it can move back and forth with the fingers. But we don’t know where the belt tensioner is to loosen the belt. With the belt disc for alternator it was no problem to find this (is right there). Weeks. Problem solving suggestions? MfG