Hello Folks
(TL;dr belt # 7PK644 NOT 7PK1635)
I went down a bit of a rabbit hole trying to get the correct serpentine belt when I had to replace my alternator.
I have seen postings here and other sites where others also encountered conflicting information about the correct part numbers.
In my case, I originally ordered the alternator and new belt from a vendor on Amazon. I checked several and most of them only had one belt listed for this application. I spent about an hour trying to get the belt to fit. It was so close that I believed that I was just not doing it right. More research led me to the others that had the same problem. It turned out this was not the correct part for my situation - the difference is only a few millimeters, but enough to prevent the belt from slipping on. The correct belt took about 2 minutes to install.
7PK1635 was the size listed on the various Amazon vendors.
The CORRECT part was 7K644 (or some listings are 7PK644):
Hope this posting might help others avoid a frustrating experience.