"L" bolt frustration & dual belts?

[markberserker]

Trying to find out if a 1982 300SD Turbo is "supposed" to have a dual belt set up for the alternator. The one I am working on has a single belt pulley on the alternator, but I have seen other MB diesels that have 2 belts. Wondering if someone put on the wrong alternator as the water pump and crank pulleys have an unused slot for another belt. Of course the adjuster with the "L" bolt is all buggered up, and the belt squeels. Perhaps the bracket itself is bent out of line? Probably the wrong belt too, it seems to fit in the pulley too deep, thank you!