Interesting Dallas nugget. Tell us more about this.
What I found so far:
North American P-51 Mustang - Wikipedia
P-51C-NT 1,750 First P-51 variant to be built at North American's Dallas plant. Identical to P-51B. Mustangs built by North American in Dallas were suffixed "-NT". 636 were supplied under Lend-Lease to the RAF as the "Mustang III".
P-51D-NA/-NT 8,200 6,600 built at Inglewood and 1,600 built at Dallas. 100 P-51D-1-NA were sent unassembled to Australia. 282 under Lend-Lease served in the RAF as the "Mustang IV".
P-51K-NT 1,500 Built at Dallas, Texas. Identical to the P-51D except fitted with a four-bladed Aeroproducts propeller. 600 Lend-Leased to the RAF as the "Mustang IVa".
P-51M-NT Same as P-51D-25-NT and P-51D-30-NT, but with the non-water injected V-1650-9A engine for low-altitude operations and sharing the cuffless Hamilton Standard propeller. It was intended to enter full production at Dallas, but the contract was later cancelled.