Hrm... I dunno... From what I remember, isn't the spitV over-modeled? Isn't it more than a match to the 109F4?
Just out of a sense of pure fun, hrm... I once had fun in realistic settings (fuel=1.0, ammo=1.0) in P51D vs F4U4. I was in the P51. We had a jolly good time.
F4u1x vs ki61 is also fun, personally. Although I had better luck in the F4U than the ki61