You are right about the kit part but unfortunately its the kit part that is wrong for my kit. From the link I posted above plus there are several photos...
"all P-51D up to P-51D-20-NT 44-12852 and P-51D-20-NA 44-72226 (c). Contrary to what has often been written, the N-9 was never fitted to the P-51B & C as the required number of modifications to the cockpit and additional parts to be fabricated was considered ineffective. (d) Update: if true that P-51B & C were not fitted with N-9 on the production line, some were nevertheless field modified with an N-9 as one of the photo of the gallery below will show"