Now Weave, I wouldn't go that far. The Mustang can do 437 in level flight. 350 is a far cry from 437.
A6M2 had a top level speed of about 310 to 320, that may be more what you were thinking of. In any case, a Zero can dive to more than 350, although I'd be nervous about taking an A6M2 to 400 or beyond. An A6M5 is quite noticably more poweful in the engine department and I would expect to get 425 to 450 out of it in a dive. Of course at those speeds the controls will be so heavy as to make the plane almost uncontrolable.
Sisu