Good day Jorn
Have a look for part numbers and inspection stamps on the parts. They identify the type and to a lesser extent the sub-model but be warned vendor parts carry vendor numbers. EG turbo-supercharger parts on the P-47 have GE numbers and stamps.
Mustang numbers are constructed of the NAA model number the part was first used on followed by five or six digit part number, and sometimes a subpart number of 1 to 3 digits - 83-31826-300 is an early wind-shield assy but wind-shield 106-318226 is used starting on the P-51D-5 NA. Later aircraft changed again
The ww2 model numbers for the P-51 include 73-, 83-, 97-, 99-, 101-, 102-, 103-, 104-, 105-, 106-, 109-, 110-, 111-, 122- etc so if you find a 106- number the aircraft was a P-51D-5 or later
To add to the confusion you may find 16- or 19- etc parts as a small number of BT-9 and T-6 parts were used on the Mustang. For a full list of P-51 NAA design numbers see
P-51 Mustang Production - MustangsMustangs.com
P-47 part numbers are constructed completely differently. 2 digits, a letter, five digits, a dash, one or two digits, and, if left or right the letter L or R. For example ing tips are 89T24000L or R. Vertical stabilizers are 89J55000-50, -51 or -52
Happy hunting
Lets know if you find other numbers and I may be able to identify them. Many companies had numbers that have distinct characteristics