Hi Chris,
Best known P-51D flown by a New Zealander was 'Isabel III' of Flight Lieutenant Jack Cleland who was attached to the 363 FS, 357 FG during late 1944.
The photo isn't the best - it is from the Wanaka Fighter Pilots Museum and shows a Mustang which was temporarily painted as 'Isabel III' for the 1998
airshow

The P-51D flown by Cleland was an early model P-51D tail No 44-13573, codes B6-B. 'Isabel III' (Cleland's personal marking) in yellow script on forward port upper cowling.
No fin fillet. RAF Green or Olive Drab top surfaces.
A few years ago Malcolm Laird of Ventura Publications
http://www.thescale.info/news/publish/index.shtml brought out a 'Classic Warbirds' book which had a chapter on Cleland in the RAF and USAAF. Isabel was the name of Cleland's fiance, later wife. As his widow Isabel Cleland was guest of honour at the 1998 airshow.
NB: A site on the 357th
http://www.littlefriends.co.uk/357thfg.php?searchString=cleland&Submit=Search which shows Flt Lt Cleland's P-51D listed as B6-V OR B6-B - chances are the code letter was changed at some point. (The Homepage is
http://www.littlefriends.co.uk/index.phpHope this helps.