P-63C:
410mph at alt, 365 at sea level
1800 hp WEP (vs 1100-1300 for P39 and P63A) = great acceleration
60 rounds of 37mm ammo (about double what the P39 had)
3 hardpoints for up to 1500 lbs bombs/fuel
Rocket rails for up to 8 5" HVARs
Historically correct, though virtually all went Lend-Lease to the Soviets.
This would provide a nice jabo alternative to the P47, FW190A8 and P38; a decent swing-role fighter.
Give it nasty stall characteristics (like the C.205 or Corsair with flaps up) so somewhat mimic real-world low speed handling issues.
Ok, I know I've posted about this before but you can't blame a guy for trying