I have a friend who crawled through the Belle in 1979, before any restoration work was done. He confirmed that everything aft of the radio room was bare metal. The radio room, flight deck and nose compartment were also mostly unpainted with dark green padding (most of which was gone by then.) The metal parts that were painted were Dull Dark Green..Model Master "Euro 1 Dark Green" is a decent match. The bomb bay was neutral gray. Here are some pics he took, with comprehensive notes:
http://www.arcair.com/awa01/101-200/awa164-B-17/00b.shtmThe Revell kits are the best detailed B-17s in any scale. I haven't picked up the new F yet..I got the G when it first came out, but it has a few "issues" that kind of turned me off.
One notable omission on the Revell F are a couple of windows in the top of the nose compartment. They included the centerline windows, but you'll have to add the off-center ones yourself. Here are a couple photos of the Belle showing the windows I'm talking about (ignore the "interior green" paint in the nose and cockpit..the entire interior was blasted with it during an earlier restoration.)
Good luck on your project!
SN