Gordon's great ADF site explains the serials anomoly; ET600 / 41-35954 was the original "Longhorn" lost with pilot Zendarski, one cowl panel was added to ET889 / 41-36243 which was lost near Kokoda as you say. There is a colour photo as it was found on this page....
go down to "CURTISS CORNER P-40E-1" ( RAAF serial A29-125 was assigned to 2 Kittyhawks as he explains).
Nick
http://www.adf-gallery.com.au/newsle...7%20Summer.pdf