"Truth be told you will not be able to find much if any real world data on 'energy' values wrt WWII aircraft, not in the post war since/definition of 'energy'..
In that it wasn't until just after WWII that a real 'standard' test was defined to measure energy and the change in energy.. "
Not strictly true Ace of Aces. A number of Fan plots (Dog house plots) for a few aircraft in WWII exist. Specifically the 109E3 and Spit I are there.
Though I do agree that general EM theory was in its infancy.
Both the RAE and USN produced some of these. The RAE document "Notes on the dogfight" AVIA 6/2366 discusses sustained turn with respect to excess power and graphical depiction of this using using Fan plots.
a 1G Specific excess power (Ps) chart for the 262 exists as well.