Having run a repair shop many years ago, even then we were seeing fake parts, some were obvious, like Motorcare vs Motorcraft, Automotive vs Autolite etc. That being said I had a line of parts in plain boxes, that were excellent quality, but unless I knew you real well, you wouldn't see them. The best was a carb kit for the Ford 2100 carbs, cost me $2.50, came in a plastic bag with an instruction sheet, no box. An Autolite CT-499D was about $9.00 list, Carter 902-857D I believe or Guaranteed 77-857D (same kit, different source) was probably $7.50. Since I guaranteed repair work, most customers didn't care what I used as long as I stood behind the work. If you were a good friend, I would sell you one of those kits over the counter for $5.00.
These were excellent knock offs, I could open all 4 different kits and lay the parts out on the counter and challenge you to find the difference. I carried AC-Delco and AC plugs for GM , Champion plugs for Chrysler, AMC and Studebaker and Autolite for Ford I had Autolite tune up parts for Ford, Chrysler I had Echlin tune-up parts as Chrysler's aftermarket support was pretty bad in the late 60s.
Bill AKA "LOBO"
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"Getting old is inevitable, growing up is optional"
Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator
Wife's 2011 Flex Limited
Daily Driver 2009 Flex Limited with factory tow package
Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413