Originally Posted By: 440Magnum
Most automakers have ENTIRELY separate operations for factory parts and replacement parts
Not in my experience -- and I used to work in the industry.
Especially for Honda and Toyota (remember the OP has a Honda), most parts stay with the original supplier for the life of the part.
For Honda and Toyota, "line" production and "distribution" production come off the same line and the same tooling with the same materials and processes.
Originally Posted By: 440Magnum
If you really are looking for exact OEM replacement- make sure it both looks the same down to small manufacturing details, AND carries the same set of numbers where possible.
Parts are frequently subject to running changes that alter their appearance, so you can't go by that.
As far as numbers go...
If Honda or Toyota changes suppliers, the part number will change.
If the part is "rationalized" (combined with other parts), or changed in any way from original production, the part number will change.
If a part is improved (this is a frequent occurrence), the part number will change.
If the part number changes, the new number is said to "supersede" the older number.
Originally Posted By: 440Magnum
Sometimes its just about impossible to find exactly what the car maker used on their assembly line out in the retail world
Not with Honda and Toyota. You just go by the part number and any "superseding" that may have occurred. Since the parts database is constantly updated, looking up the old number will result in the new number coming up.
Maybe the domestics do things differently, I don't know. For Ford or GM, what you say may well be correct. The engineers at the Tier-1 suppliers I used to deal with had a much lower opinion of the domestics than of the Japanese. This opinion was based on the differences in how the imports and domestics handled design and manufacture of parts, and especially on how the two handled defective designs.