Following opinion exist.
http://japaneseaircraftofwwii.blogspot.jp/2015/03/mitsubishi-a7m3-j-variant-of-reppu.html
The proposed A7M3 variant of the Reppu and the land based sub-variant (the A7M3-J) were to be powered by the Mitsubishi MK9C eighteen cylinder radial engine that was rated at 2,250 hp on take-off, 1,800 hp at 5,000 metres and 1,660hp at 8,700 metres. Armament comprised of six wing-mounted Type 99 Model 2 20mm cannons (for the A7M3) and four wing-mounted 30mm Model 5 cannons and two rear-fuselage mounted obliquely firing 30mm Model 5 cannons. The dimensions of the A7M3 and the A7M3-J were supposed to be identical to their predecessors however the weights and also the wing loading of these models were different to those of their predecessors. For the A7M3 model, the weight when empty stood at 3,392 kg and when loaded it was 5,040 kg, while the wing loading was 163.3 kg per square metre. For the A7M3-J model, the weight when empty stood at 3,955 kg and when loaded it was 5,732 kg, while the wing loading was 183.1 kg per square metre.
The Combined Fleet website says carrier fighter but, oddly, other sources say that the A7M3 (Model 23) was based on the airframe of the A7M2 (Model 22) but without the wing-folding mechanism.
Either way, the A7M3 was powered by a Mitsubishi MK9C (Ha-43-31 with three-stage two-speed compressor - 2,250 hp T/O, 2,000 hp at 1,800 m, 1,800 hp at 5,000 m, and 1,660 hp at 8,700 m). Armament was increased to six 20 x 101 mm Type 99 Model 2, all wing-mounted.
By contrast, the land-based A7M3-J was to be longer (presumably ahead of the firewall), have greater wing area, and would be powered by a turbocharged engine (Mitsubishi Ha-43-11 Ru). Armament was to be six 30 x 122 mm Type 5 cannons (2 x oblique fuselage-mounted, 4 x wing-mounted).
Other sources say that the A7M3 and A7M3-J were both powered by Mitsubishi MK9Cs, differing only in the armament fitted.
But accoding to Mitsubishi's data, MK9C's super charger was a single stage three speed supercharger.