Evan, 'C' wing, no .50 cal, cannon mounted inboard, faired stub housing outboard. Wing bulges longer and slimmer on the 'E' wing, broader and higher on the 'C' wing. (Those on the Vb were shorter, and mounted further aft, as this covered a drum magazine.) The 'C' wing could also be seen with a much broader, flatter bulge, designed to cover the BFMs for two cannon, but this was mainly employed on the MkVc.
Wings were made with ejector port openings, but plated over as required depending on armament fit.
Spitfire ML407 was (and is) a MkIXc, (referred to during the war as a MkIXB) and had the cannon mounted inboard. This was the personal aircraft of Johhny Houlton, of 485 Sqn, and the history of this aircraft, along with some pics, is shown in his book 'Spitfire Strikes' (a great read, got it on my shelves).
This aircraft was restored to flying condition, and to two-seat configuration, by the late Nick Grace, and is operated today by his widow, Caroline Grace, and still caries the 'OU-V' codes. Johhny Houlton got to fly in his old mount during a visit to the UK in the 1990s.
The book is worth reading if you can get a copy Evan. Covers some good stuff, including his part in the development of the Gyro Gun Sight, which he'd been using from 1943, long before Britain passed details to the USA for the production of their K-14.