iirc I did research it. It was on a prior post here. The goodyear website doesn't specify Montero, I was going off what you said you had run for years.... ?

found correct item from Febi Bilstein part number W0133-1618848, ordered thru Auto Parts Network. Having it overnighted, as I cannot wait any longer to get this pulley on. When I receive part I will let all know if its the answer to my problem. Cost is $40, plus I overnighted for additional $16. Will advise.
anybody have a 91-93 benz 500 series they need a pulley for...cheap ?

Part arrived and it took less than 10 minutes to replace worn pulley. After several attempts tightening the adjuster head bolt on "center" idler pulley, (again, one at 5pm using the alt as a clock)she now makes NO noise. So nice driving down road without the squeal ! I also learned (and correct me if I'm wrong)that I needed to make sure the adjusting head bolt was pretty tight to alleviate the tiny little squeal still there when I first installed new idler pulley.
I'm hoping this "tightening" sequence doesn't mean that perhaps the alt pulley is making some noise and because I tightened her up pretty good, it quieted it down ? Can anyone tell me just how tight the serpentine belt should actually be ? Mine is on there pretty snug.

The squeal is back. Two days of silence . Its not as pronounced, but its there. It will go away after a bit. Now it's got to be narrowed down to either the alt pulley or (gasp!) the water pump ? Accepting advice....