I was bored, so I did some high altitude top speed tests

All planes tested with 100% fuel and ammo loads.
Plane(guns) - TAS at 25000ft with WEP on.
P-51D(6x.50) - 435mph
Bf109G-10(2x13mm,1x20mm) - 425mph
Spitfire MkIX(2x20mm,2x.50) - 415mph
F4U-1D - 410mph
La-5FN - 400mph
C.205(2x12.7mm,2x20mm) - 400mph *retest*
FW190A-8(2x13mm,4x20mm) - 380mph
N1K2-J - 350mph
B17G - n/t
C-47 - 230mph(20,000ft)

I suspect the FW190A-8 is a bit slow? Maybe the N1K2-J too. Then again, both engines did have a reputation for losing power at high altitude.
[This message has been edited by juzz (edited 12-13-1999).]