Anyone know which is the ideal one to get?

According to RockAuto:

GATES 38091 : $23

CONTINENTAL 49073 Accessory Drive Idler Assembly Grooved Pulley; Belt Type: 6 rib Poly-V, Grooved; Non-Flanged; Thermoplastic; pulley Width: 26.5mm; Bearing ID: 17mm; Bearing OD: 63.5mm Info
Accessory Drive Idler Assembly : $26

ACDELCO 38082 {#89056015} Belt Drive Pulley $27

Are the idler pulleys the same on the NA? I noticed the ACDELCO and CONTINENTAL has the same part number on the NA, but the GATES does not. Then when you look up the C32 AMG there are no idler pulleys available?

Mercedes one is 1122020119.

This looks to be it: http://www.ebay.com/itm/MERCEDES-BENZ-1122020119-GENUINE-OEM-PULLEY-/161527980999?hash=item259bd163c7&vxp=mtr
$64 shipped.

Any help would be great thanks. If needed I will just get the Mercedes one even though it is double the price. But if I can save money I am game.

 

Do you need the grooved one next the supercharger pulley or the smooth one that's down lower? If you need the grooved one this is the part# 120 200 04 70 . It has 8 grooves not 6. That one on ebay 1122020119 is the right one if you need the smooth one.

 

Whichever one goes bad. Yeah I checked my ride out and the part number stamped on it is 1202000470 like you stated. I have a new NSK supercharger bearing on its way too. Thought I would do them both.

this correct?

http://www.ebay.com/itm/New-Mercedes-Benz-W140-S600-R129-SL600-Belt-Pulley-1202000470-/281424174166?hash=item4186301c56&vxp=mtr

 

thanks again for that post. I ended up ordering both to be on the safe side.