Here's some Technical information:
Ki. 43-Ia 35 built
Ki. 43-Ib 45 built
Ki. 43-Ic 716 built (this includes all Ki-43-I series)
Ki-43-IIa 2524 built
Ki-43-IIa-Kai Tropical 300 built
Ki-43-IIb 1531 built
Ki-43-II-Kai 500 built
Ki-53-IIIa 1098 built
Ia had twin 7.7mm machine guns, Ib had a 7.7mm and 12.7mm, every other version in operational numbers had twin 12.7mm's.
Most flew with a pair of 30kg bombs, only later versions carried a pair of 250kg bombs.
None flew with 20mm cannons except the Ki-43-IIIb which only 2 were created and flew in June 1945.
Early versions used the Ha.25 engine with 950 hp, later models used Ha.115 with between 1120 and 1150 hp.
All were built by Nakajima except for the two prototypes of the Ki-43-IIb (20mm version) which was made by Mitsubishi.
Sources: Ki-43 by Richard M. Bueschel (Schiffer military history book) and Profile Publication number #46, Ki-43 Hayabusa