The story is, of course, fiction: written to go with some (very nice indeed!) photos of a model Train Master painted in Santa Fe livery. All VERY well done.
Fairbanks-Morse engineers undoubtedly thought about possible enhancements to their locomotive designs, and after the company stopped building locomotives they DID produce a 3600 horsepower version of their engine for stationary service. (Unlike the fictional engine in the story, it got its increased power by turbocharging, not by adding extra cylinders beyond the 12 used in the Train Master engines.) As far as I know from a variety of Fairbanks-Morse histories(*), howeverr, they never built a test or demonstrator locomotive more powerful than the 2400 horsepower Train Master. The technical specifications suggested in the story are unlikely-seeming for a couple of reasons: (i) a 20-cylinder Fairbanks-Morse engine would have very long crankshafts (so it would have presented a significant engineering challenge to develope, and might have had bad problems operating on a less than perfectly rigid support such as a locomotive frame); (ii) single-engined 3000 horsepower and up diesel electric locomotives only became practical after the mid-1960s introduction of alternating current generators and solid state rectifiers, and would have been a huge challenge with 1950s electrical technology.
The Santa Fe did introduce a high-speed Chicago-Los Angeles container/trailer train in the late 1960s (early 1970s) called the "Super C," but the name was, I think, chosen as a reference to their famous "Super Chief" streamlined passenger train, not as a follow-on to an earlier "Super-B".
But it's a nice story and very well done!
(*) "Trains" magazine published a number of interesting historical articles by Robert Aldag, a former Fairbanks-Morse employee. John S. Kirkland's book, "The Locomotive Builders, vol. 1: Fairbanks-Morse and Lima" is unfortunately out of print, but contains a complete list of Fairbanks-Morse diesel locomotive production.