A bit more information

I’ve just found my copy of “First over Germany”. The P-51’s serial is quite visible in my copy and is 43-12457. If you google this you’ll find a fair bit of information about it. It was coded 7F-F and belonged to the 370th FG at one time. It seems that it kept the 7F- codes when it joined the 306th BG. As Dan J said above, by 1945 it would have been used as a hack.