back in the day, i worked at a body shop [1968-1972] whose specialty was rebuilding totals. [this was pa.]
this involved front clips from the dash forward, rear clips from the rear post of the door opening, and everything in between.
the paperwork involved required state trooper inspection to make sure nothing "funny" was done. these guys were in and out several times a week.
back then, there was no such thing as a salvage or rebuilt title, so all cars got a clean title showing nothing but the mileage and the appropriate serial numbers.
we always made sure the customers knew these were rebuilt, and usually had requests for specific makes and models.
lots of muscle went through our shop with no legal hassles whatsoever.
every single customer [while i was there] was more than happy with their purchase because of the cost savings over new, or very low mileage [almost new] used.
as to the tag question, that depended on how much was replaced, and which was the best car to repair out of [the] two used to create one.
the tags not used, as well as the title corresponding to that tag, was turned over to the trooper upon final inspection of the rebuilt vehicle.
this is just my experience
Pretty much my same experience working in the body shop back in the 70's, clipping vehicles front or rear, mostly insurance work, some insurance companies also brought along LE, but mostly to collect the paperwork or tags used from the donors, and or confirm the donors were dismantled/destroyed, there were a few cases where a donor vehicle (usually auction buys) were in better shape than the shop purchased vehicle/customer's vehicle and basically a rebody was performed as it was just easier to move everything over to a clean donor.... and if you think the customer/buyer was informed, think again, they were just pieces of merchandise for sale/trade or customer's rebuilds.... and we did everything from grocery getters, trucks, muscle cars, vettes, etc, etc
