I'm aware of flight tests done on the final WVa ANG P-51 in "WW2 config" in the 1950's, before they donated the aircraft to WPAFB.
Then there's Navy flight tests of both the P-51B and P-51D, Army flight tests of the initial P-51, a botched British flight test that they screwed up, a number of more recent tests done on surviving P-51's (some of which are done on the plane in WW2 config) and then there's any number of less formal flight tests done by pilots and such. That's just for starters; other tests exist.
In other words, there's probably more good info available for the P-51 than for any other WW2 fighter.
I'm not sure how much of it is available online.
J_A_B