There were only two A6M1's constructed, both of which were test airframes. Early war Zero's that operated in China were the A6M2 model 11. Early war means 1937-39/40 area, not 41-43. By the time of Pearl Harbor, the A6M2 model 21 (later changed to A6M2b) was in service. The number after the designation A6M2 indicates the number of engine and airframe modifications (pronounced one-one or two-one, etc.) respectively. Thus, an A6M2 model 21 had two engine changes (mods) and one airframe change.
Later on, the model designation was dropped and zero's were referred to as just plain A6M5 or A6M5 ko, otsu or hei; a,b and c respectively. Incidentally, the A6M2 and A6M5 were on the production lines at the same time, although by different manufacturers. Can't remember if it was Nakajima or Mitsubishi that kept the A6M2 production going.
My references indicate that the AVG did use P-40B's and C's but also had a number of those strange hybrid birds called H-81's I believe.
[ 08-22-2001: Message edited by: EDO43 ]
[ 08-22-2001: Message edited by: EDO43 ]