A friend if mine with this car has an a/c ompressor clutch that is siezing up. He wants to get a shorter serpentine belt so he can bypass the a/c till he gets around to fixing the clutch. Problem is, neither Autozone nor Advance Auto Parts list the belt assuming no a/c the only kind of belts they sell are for Bonnevilles equipped with a/c. Yet, the belt routing guide shows how to bypass the a/c compressor. Question is, how can he get the right sized non-a/c belt?
He can use a string to measure the length the belt would be using the non-a/c diagram, and take that measurement, along with his original belt, to a parts store and have them match one for width and length. Shouldn’t be that hard to do. I believe many manufacturers have the length (in millimeters) as part of the part number for their belts.
Now why didn’t I think of that. I guess that’s why they pay you the big bucks 
Thank you NYBo.
One more factor to consider: Make sure the belt tensioner has pressure on it when the measurement is done. Otherwise the measurement will be too long and the belt won’t be tight.