[William]

In some cases an alternate part number is listed in the Assembly Manual with the description 'opt'. There are at least 40 examples of this in the '69 AIM with a few having 3 acceptable part numbers.

Having worked in automotive supply chain, a discrete part with multiple sources may be furnished under one part number-the 3960314 sheet metal fastener is found with different supplier head markings and were co-mingled in production stock. In the case of functional parts, a decision has to be made. Rochester/Casco lighter parts were both used in production but under different part numbers. Separate production stocks would be maintained.