You could always take a look at
WWII Aircraft Performance
There's tonnes of info on planes on that site... not just Brit planes.
Also, theres lots of information on weights and wing area there and all over the web. Look that up and you'll be able to find out wingloading from waht you know (which is loaded weight divided by wing area). That's just one of the main factors on turning performance.
Also, radius isn't the biggest thing in turning. Turn RATE is very very handy for turning battles. A Spitfire, for example may turn extremely tightly, but if an F4U drops its flaps at the right moment, it can actually turn FASTER than the Spit, that is, complete more degrees of a circle faster, which allows it to outturn the Spitfire. The Bf-109, also, could turn very tightly even due to its large wingloading, all thanks to wing slats which smoothened the airflow over top of the wing in high Angle of Attack (AoA) maneuvers. So a plane that will turn faster won't necessarily have to turn tighter to win the contest.
Main factors to turn performance include wing loading, power loading, drag and sometimes, wing/flap design. This is so due to the fact that US planes have the top notch flaps of all the countries; slotted flaps (which takes air from under the wing, pressurizes it and shoots it over the top of the flaps to gain lift), Fowler flaps (flaps that not only bend down for greater AoA, but also push outward, increasing wing area), and the split-flap (kinda like the Spitfire's flap. splits the bottom half of the wing downward. not the best flap).
In your arguement, I'd have to say the turning radius of each plane, from smallest to largest are:
P-39, P-40, P-51, P-38, and P-47.
My F4U should fit somewhere in between; just worse than the P-40.