Is it a simple fix of finding a larger serpentine belt, or am I going to have to buy a 143 or 150 amp alternator that will fit a 300SDL W126 OM603 engine?

Unless I'm mistaken, I just learned the hard way that an AL129x 115 Amp alternator will not fit a 300SDL W126 OM603 engine simply because the serpentine belt is too snug.

I purchased a '92 Saab 9000 AL129x alternator from eBay and began wiring it into my 300SDL. Everything bolted in normally, and I was ready to go after upgrading the wires, but when I tried installing my serpentine belt, it seemed to be slightly too tight. I couldn't get it back on even after releasing some slack with the spring tensioner (I unbolted and released the spring tensioner when I pulled off the old alternator.)

The serpentine pulley from the stock alternator (AL65x) seemed to match up with the replacement (AL129x) when I eyeballed them together. The only thing I can think of without dismantling everything again is that the distance from the pulley to the mounting bracket is slightly larger on the AL129x.

I've read several posts on this forum that said it had worked and others that said it wouldn't work.

Am I going to have to buy another 143 (AL0162X) or 150 Amp (AL0766X) alternator from a V8 W140 now and be stuck with an AL129x that I can't use? If so, are these the cars that I can pull one from since they all have a V8 engine?

1991–1993 400SEL
1993–1998 S420
1991–1993 500SEL
1993–1999 S500
1994–1998 S420/CL420
1992–1993 500SEC
1993–1999 S500/CL500

Last Question: If I buy a 143 or 150 Amp, do I need to modify anything, change any spacers so the serpentine belt will line up properly, or change the pulley from the stock AL65x? Do I need any special tools to change this pulley out?

Thanks for any suggestions or help. I don't want to make another mistake in getting the wrong alternator or making an improper modification.