A speaker from Local Motors came to the GAA conference in Clemson last year and then I was able to go by their facility in Phoenix when I was out there for a conference. At the facility, they had vehicles that were in the middle of assembly, but they aren’t moving down a line. They are built one at a time, many times with the participation of the person who purchased them. Some parts of the vehicle are 3D printed, but the large printer was not in Arizona when I went by (they have several different facilities that share the 3D printer between them).
At Local Motors, there is a huge area set aside for local creatives to come and prototype their own ideas. Parts and pieces that are mid-construction are all around the shop room floor.