Check out this article at
RetroMechanix.com on a P-51D Mustang which was tested with a pair of unusual streamlined 150 gallon ferry tanks at Eglin Field, Florida in 1944-45:
The object of the tests was to determine the safe ferry range of the P-51D airplane. The article features 20 photos of the installation, as well as scans of the actual report itself. I've not seen this type of drop tank installation on a P-51 before, though they are described as "standard P-51B 150 gallon auxiliary tanks" modified for use on the P-51D.
Also, this article and all prior ones now feature thumbnails for easier navigation of the images.
-Jared