Just to mention that the aircraft in picture 6 (next to last) is a norwegian Northrop N3PB used for anti-submarine (and anti-FW Condor-) patrols from Iceland in 1941-42 (RAF 330 sqdn). These were ordered before 9. april 1940 but after the invasion were delivered to the in-exile norwegian...
Morgan and Shacklady's "Spitfire - The history" states that the tanks were 30 (or 29) gallons, except for the two 70 gallons tanks fitted as a mock up (the second picture from Wurger) for a solution to the problem of ferrying spitfires to the mediterranean. I don't think the latter were actually...
I actually did a kit-bash of this turret fighter a few years ago, from figures in Morgan & Shacklady's magnum opus "Spitfire - the History". I based it on the old airfix kit with a self made turret and canopy. It seems that the rest of the version would be almost indistinguishable from a normal...