The first use of the 7" block style passenger car lettering was on the “Southerner” and “Tennessean” trains of 1941. The SRHA archives contain a letter from Pullman-Standard asking how the railroad wanted its new lightweight cars to be lettered. At first, the Southern had no idea. As EMC had already created 7" “SOUTHERN” lettering for the E-6s, a copy of that drawing was sent to P-S to be used.
Most “stencil” (lettering placement) drawings and drawings for individual full size letters and numerals; Roman, Official car and block are in the SRHA archives