Raptor, if the texture is actually somewhere on that skin, this will help you find it.
Temporarily replace the p51side skin with this image and build it into the terrain. Now when you view the model, you can use the letter/letter-color/background-color to determine wher the texture falls.
There are no repetitions of the letter/letter-color/background-color combination, so when you see (for example) "Red M on Black" on the spinner, you'll know exactly where to look.