I looked at the thread that SRT-14 did on changing a convertible over to a 1970-up. His article is mainly focused on building a shaker hood but one of the first pictures he shows is the rear section of the car mocked up with the 70 rear on the convertible. It looks like he made a vertical cut straight down the quarter about 4 or 5 inches ahead of the side marker but it's kinda hard to tell because the vert and the donor appear to be the same color. That was kinda the route I was thinking about and seems to be the most logical. I would love to get a more detailed look at that part of the build but it looks like that is the only picture he included on that part of the transformation of the rear quarters.
