Auburn 680 Fan & Generator Drive Belts

I didn't think any parts stores would have listings that far back. I tried Jegs.  No belts listed for 1929, but they did have Gates belts for 1930 6-85. Then I checked Gates' site.  I will order from whoever can get them to me quickest.  The generator belt is a 5L as I thought.  The fan belt uses a 15A cross-section.  I checked the length around the pulleys with a cloth tape and what Gates listed looks about right.

I need to buy the drive belts for the fan and generator on my 680.  I cut the tattered old ones off before starting the rebuild.  I don't have them any more.

I know how to calculate the lengths, but I'm not sure which width to get- ie 4L, 5L or other.  The widest width of the v-groove on the pulleys is approximately 3/4".  So I'm thinking "5L" or "B".  Do any of you used cogged belts?