X2 on referencing other side. When I did my lower quarters, I did the worst one first, so I had the shape of the better one to work from. (Yours are way better than mine were)
Wherever possible, build it up in layers similar to original. ie front /back pieces you took off. Easier to make the shapes and it will be stronger. Don't know specifically about that year/model how they join, but usually its an outer skin and a trunk extension drop-off. Not sure how your back section(s) connect. Thats not a very big area, so you should be able to follow the existing edge lines for most of it. Did you take any pics before you started cutting? If not, get your camera snapping. Get tons of pics, then when you are ready to work on a specific area take some more. Can never have enough reference shots. If you don't have a pic, check other build threads for some of the area.
