To close out this thread and help others in the future here's what I did.

Bought multiple belts with the intention to take back the ones I didn't use. Well, they were all extremely to short.

Faced with the possibility that I was going to have to put that damn pump back on so that I could drive to the parts store was not a very appealing option to me. So I reinstalled the original belt, minus the air pump and was surprised to see what a close fit it was. After a adjustment of the belt tensioner the original belt was nice and tight.

So there you have it guys, on a M104 you can remove the pump and use your stock belt.

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'94 E320 with 272,000 miles. '92 500SEL 133,000 miles.
Mods to the '94: TomTom GPS in place of ash tray, Auto Dimming Mirror ,Memory seat, DEI 545T Auto lamps, DEI 530T Auto Up/Down Windows, DEI Remote Start, Motorola Bluetooth® Car Kit, Built in phone charger using factory phone wiring, RainTracker Rain sensing wiper, Keyless Entry, Ambient lighting of center storage compartment. Soon: factory heated seats, REST
Mercedes-Benz is my addiction of choice.
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