Fastback Resto
Great project! Most sheetmetal is stamped out at the same Taiwan plant anymore so it doesn't really matter who you buy from other than price, service, and shipping rates. The shipping can be as much as the part! They're generally thinner than OEM and the body lines aren't as crisp. If you don't have to replace the entire quarter, then don't - get patch panels or fab what's needed.
Anyway, the main resto supply places (Year One, Paddock) sell skins at inflated prices. Other places to check would be: Goodmark, Shermans, and Auto Body Specialties. You should be able to find quarter skins and 1 or 2 piece trunk floors.
Good luck and take care of that shiner!