Go to the Navi-Gates application on the Gates belts website.
They show all the different configurations and their numbers for the belts.
It used to just be a page....
Of course now they want you to load their junk onto your phone!
https://www.gates.com/us/en/knowledge-center/mobile-apps/navigates.html
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.