wusak,
You are absolutely right on the Spit XII. With the Griffin IV the Spitfire speeds were 375/4600ft. and 389/12,800ft. and rate of climb 4,960fpm/1,900ft. But as I said, only 15 combat Spitfires had this engine. I would guess that the Griffin III engined Spitfire which made up the majority of Mk.XIIs had performance somewhere between the Griffin IIB and IV models.
The Mustang I used the V-1710-F3R and F21R engines. If I am reading the charts correct there best heights of performance are 7,900ft. and 4,000ft. respectively. The maximum speeds of the Mk.I were 392mph/7900ft. and 378mph/4,000ft. respectively "officially". However, as I said, overboosting of the early Allisons with 8.77 supercharger gearing was pretty much "standard operating procedure" in the field. Speeds of 400+ and 385+ for these engines were highly likely.
A/C.........S.L...........5,000ft.....10,000ft...15,000ft.
F4U-1...348/3160....344/2510..359/2450..378/2300
F4U-1a..365/3210...377/3120..397/3020..415/2575....(with water injection)
One note: I am not sure when the USN or USAAF started using water injection for there aircraft so the F4U-1a figures may not apply.
If anyone has this information, I would greatly appriciate the insight.
Thanks, Jeff