First, never mind the location of the Train Number Indicator boards. Lionel's Legacy version of the GS-4 was the "as delivered" version with the small "Southern Pacific Lines" lettering high up on the tender sides, and the Train Indicator Boards in the forward location on the skyline casing. In 1946, the SP stopped using that "Lines" lettering, and had already moved the Train Indicators back midway on the skyline casing.
Now, the "what's wrong" with the Lionel Legacy GS-4, in in the running gear, i.e. the main connecting rod on each side. Lionel used the running gear mechanism from their earlier GS-2 model, and the main rods on GS-2 locomotives where smaller than the really big main rods on the GS-4/GS-5 class locomotives.
I should add that, although I have this Lionel Legacy GS-4 model and model in the mid-1950s, I still like how this model sounds and performs. I am still thinking about having my custom painter buddy of mine, remove the "Southern Pacific Lines" lettering from the tender and then re-decal the tender to reflect the "post 1946" large SOUTHERN PACIFIC lettering. However, I still don't know what to do about the forward mounted Train Number Indicators.
Also, for what it's worth, those Train Number Indicators, always reflected the train number. Rarely did the SP operate the "Daylights" on Extra Trains, and when they DID need additional sections of a given passenger train, the Train Number Indicators carried a
"1-98" or "2-76" indication. As a general policy back in the 1940s & 1950s, the GS class locomotives where not used in "Extra freight" service. There were, however special Second Class fast merchandise/reefer trains on the SP, which used GS class locomotives (especially GS-4/GS-5, due to their size & power), and those were three digit number trains, and those numbers were carried in the Train Indicator Boards.
OK, I know,,,,,too much information!