Same here. I remember one guy that had a pretty regular business going in the early 70s buying wrecked Japanese cars and cutting them right across the middle to match a good front half with a good rear half, and then repainting it and selling it.
Which while being in that business, had to document the
changes of two "salvage" vehicles, and the finished
rebuilt car was titled as "salvage" using the vin plate
number. Not the vin stamped anywhere else.
The reason for the "salvage" title is typically due
to an insurance company's settlements on
wrecked or stolen vehicles being placed back on
the road.
Most don't mind a vehicle titled as such if the
work to make the required repairs are sound.
The purist searching for a numbers matching
holy grail would avoid a "salvage" titled car.
If one is buying a car with
multiple vins discovered,
(even those stamped on
engines and transmissions)
it's in their best intrest to
run those numbers thru
your insurance company,
and your state police.
Speaking from experience.