In the early months of 1942, with the clear superiority of the Focke-Wulf Fw 190 over the Spitfire VB, there was much pressure to get Spitfires into production using the new two-stage supercharged Merlin 61 engine. In September 1941 the Spitfire Mk III prototype N3297 had been converted by Rolls-Royce at their Hucknall plant to take a Merlin 60, which had been specifically designed for use in the Wellington Mk VI high altitude bomber.
The performance increase was described by Jeffrey Quill as a "quantum leap" over that of the Mk VB and another Spitfire airframe.
The Mk XVI was the same as the Mk IX in nearly all respects except for the engine, a Merlin 266. The Merlin 266 was the Merlin 66 and was built under licence in the USA by the Packard Motor Company. The "2" was added as a prefix in order to avoid confusion with the engines, as they required different tooling. All Mk XVI aircraft produced were of the Low-Altitude Fighter (LF) variety. This was not determined by the length of the wings (clipped wings were fitted to most LF Spitfires), but by the engine, which had been optimised for low-altitude operation. All production Mk XVIs had clipped wings for low altitude work and were fitted with the rear fuselage fuel tanks with a combined capacity of 75 gal. Many XVIs featured cut-down rear fuselages with bubble canopies. On these aircraft the rear fuselage tank capacity was limited to 66 gal.
The conversion kit is tailored to the Airfix 1/24 Scale Spitfire Mk IX