Has there ever been any research into the top scoring individual aircraft
(not type) of any era? Presume it would be WWII.

It would seem that the only confirmed example offered is the Brewster flown by
Hans Wind which was Finnish Air Force serial number BW 393 which in my source
is credited with 41 victories. Another Brewster, BW 364 is credited with 36.

Quote from my post at Dan Ford's Brewster-site:

Brewster (Finnish serial) - number of aerial victories - total hours
flown - pilots and their personal score with the airframe

BW-352 - 18 kills
BW-353 - 20 - 562h 45 min
BW-357 - 16 - 802h
BW-364 - 36 - Ilmari Juutilainen 28
BW-366 - 23 - Jorma Karhunen 14
BW-384 - 18 - 729h 05 min
BW-393 - 41 - Eino Luukkanen 7, Hans Wind 26

jok