I have to suggest Tamiya's 1:48 A6M2
It's a nice big, detailed kit, five paint schemes (including a Pearl attacker), and it costs about $13, making it one of the cheapest Tamiya kits I've ever run across.
I'm more of a navy fan, so I haven't built a P-40 since I was little (actually my first kit I built on my own was the old 1:32 P-40, almost put me out of the hobby!) so I don't know just what to suggest there.
Anyway, here are the versions of the Zero...
the A6M1 Model 11 was the prototype
the A6M2 Model 21 was the type of Zero that was used in the attack on Pearl
the A6M2-N was a floatplane version of the A6M2 Model 21 built by Nakajima, codenamed "Rufe"
the A6M3 Model 22 was a clipped-wing version of the A6M2 with a better engine
the A6M5 Model 52 was the most heavily produced version of the Zero having larger wings than the A6M2 and the engine of the A6M3
the A6M6 Model 53c was an upengined version of the A6M5 with an extra machine gun
the A6M7 Model 63 was a fighter-bomber variant