Someone asked for the belt size for a 603 without AC compressor. I think in this case he wanted to run the car without the AC compressor while sorting out a bad clutch bearing.

I don't have the answer but this fellow looks to have such a belt -

http://www.peachparts.com/shopforum/showpost.php?p=1866395&postcount=246

Sixto
87 300D

Not familiar with the 603, but I have found that auto stores have successfully found this conversion for me since I almost always take out my a/c (they were more recent cars however)

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