In late 1942, the British and the U.S. sucessfully tested the Rolls Royce Merlin V-12 installed in a P-51 (NA-91). The NAA production plant at Inglewood, Ca would be at full capacity building the new P-51B. NAA decided to expand their plant in Dallas, Tx to build more P-51Bs. The B models built in Dallas, were re-designated P-51C.

In all 1,750 P-51C models were built. The NAA model #s were NA-103 and NA-111. The first C models were P-51C-1NT (NT for Dallas, NA for Inglewood). These had the first Packard built RR Merlin used in the Mustangs, the V-1650-3. The fuselage tank was added to P-51C-1s and then renamed P-51C-3NT. Later the more powerful V-1650-7 Merlin was introduced in the P-51C-5NT and -10 blocks. Alternate air source was added early on in the first block of P-51Cs.

The P-51C suffered the same problems as the P-51B with gun jamming and poor visibility to the rear. As with the B model, these problems were fixed at the factory and in the field.

Deliveres began in August 1943, later than the B model. The P-51C had to wait until the Dallas plant was ready for production.

Specification for the P-51C were identical to the P-51B.