MPC changed the body style on each F3 it made up until the late 70s
The 1st one, made in 73 is pretty much like a late postwar 2383 only w/ no vents on the lower part of the nose.
The Milw & D&RGW units are missing a set of vents on the side - only 3 while the B&O & postwar units had 4,
The changes went on unit there was just 1 vent, towards the rear of the body & ribs were put in on the lower part of the body ( similar as the Alcos). The B units did not have the ribs, but at some point lost the 2 vents on the side of the body & went to one. Lionel restored pretty much all of the original detail w/ the PWC F3 series although the Texas Special reissue B Unit only has one side vent. The only thing that has not been part back, IIRC, is the door detail on the nose, which was taken off when postwar Lionel made the 2242 New Haven F3s in 58
