So, cars are, at this point, just a hobby for me. Let's just say my real job makes certain "capabilities" available to me. If you folks want to determine fake vs. real stampings, broaches, etc., buy a Thermal IR camera. There is no way to hide alterations to metal from Thermal IR, you will see any additions, welds, cracks, whatever is not originally poured on the readout plain as day. They aren't cheap, but given all the stuff I see on here about questionable authenticity, that's your ticket.
Here's a REALLY good one. You can however get them significantly cheaper....