B Models built at Inglewood California, C models in Texas. C production ran a bit longer to honor RAF contracts. Same bird inside and out. malcom hoods started on some of the first B models and were in use on some of the Group leader and FL birds as early as March 44. Blakeslee had one on his bird with the 4th. Obviously England based RAF Mustang IIIs had them, but interestingly enough MTO based RAF Mustang IIIs did not.