If the part was produced "in house" they appear to be fairly uniform in finish. Vendor parts that could come from different suppliers tend to vary more. Nuts bolts, screw came from one supplier so they remain pretty constant. Over the last 35 years I have taken apart a lot of cars, some restored (as I call it), some parts, had a few true survivors.
All that work to clean and detail the underside to perfection, loses some of its value IF you drive it. I do so to preserve the car, that's all. But I appreciate the extent some people can go to trying to restore it all back to OEM day 1 perfection!
But I have never cared about the "show car " restored to OEM status, just wanted a solid car that looked good, that drove good!