[Grolar]

Since you're also a 80 owner, there's been a bunch of threads about rear drawers i the 80 section, including mine. After putting together a quite heavy all plywood setup, I think that If I had the fab skills and money, I'd go for an aluminum frame.
Regarding the 200, I'd be very careful not to mess the rear of a $$$ truck (scratches on the panels, for example), but would love some pics of the fabbing process. Good luck.