The guy who did the body work on my 69 used lead. After it was blasted he showed me the original lead joints from the factory.
He leaded in both quarters after they were mig welded. He also used lead on the trunk extension part which had a lot of rot.
I do know he used a skim coat over the lead for any pin holes in the lead.
I watched him do some of the work, the vertical joints are tricky for sure
This guy worked in a GM plant back in the day and did body repairs on cars that were accidentally damaged during assembly
He told me the hood he used filler and not lead.
When I asked him how much body filler he used on my car he told me he bought a gallon.
I thought that was a lot and he laughed, he told me three quarters of that was sanded off
He told me what you see on TV can be misleading, he told me some of these cars are wiped front to back with filler.
Id guess lead is still being used but is a lost art mostly