Dudley Henriques wrote:
The only viable method to accomplish individual comparison is an energy format at 50% fuel resulting in specific energy curves on each aircraft for overlay.
k5083 wrote:
Any such comparison using modern warbirds is of course greatly distorted by many things including lighter weights and other changes in the planes, habits and expectations of modern pilots, and the need to stay comfortably within each plane's envelope.
IMHO, these are the most important quotes of the thread so far.
Since the OP specifically asked "what the great U.S. fighters where capable of", and thankfully NOT the much-debated "who would win" question, it's actually a relatively simple question to frame.
As Dudley mentioned, the "modern" fighter pilot uses Energy-Maneuverability charts, invented in it's modern form by John Boyd and developed for specific aircraft by engineers and test pilots, to actually yardstick performance capabilities in dogfights. E-M diagrams show the performance measures that matter in a 1 v 1 dogfight: turn rate, turn radius, speed, and ability to maintain those turns given the airplane's available power.
Although it's tough to read, here's an E-M diagram for a T-38 just so those who have never heard of one can see it:

Overlaying the E-M diagrams of two aircraft can show areas of the performance envelope where one aircraft would have the advantage over the other.
Even then, though, the E-M performance is just one of MANY factors in the equation. This is why the "who would win" question/argument is such a futile one. In real life, the most important factors in determining the winner of a dogfight are luck/timing and pilot skill (as other posters have alluded to but not explicitly stated). Many times in documented history has an aircraft that is significantly lessor on paper bested it's opponent because of these two factors.
Bottom line is this: it is simply impossible to perform a comparison like this on paper and determine a "winner"...but you certainly CAN determine which aircraft performed better in measurable factors.
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ellice_island_kid wrote:
I am only in my 20s but someday I will fly it at airshows. I am getting rich really fast writing software and so I can afford to do really stupid things like put all my money into warbirds.