Designating GE industrial locomotives just by weight can be misleading.

The "45 ton" came in four generations - the early 43 ton with an earlier traction motor design and side-rods, the 45 ton with a more streamlined cab and hood, the same but with sealed beam headlights and chain drive instead of siderods, and a "narrow hood" design with newer engines and back to side-rods. All only had one traction motor per truck, and a pair of Cummins engines at 300 bhp (a little more for narrow hoods). These were only geared for 20 mph max, and pretty much limited as industrial switchers though a few short-shortlines used them for road power.

The "44 ton" was the result of a 1938 decision making them the largest locomotive that could be operated without a fireman, resulting in many Class 1s buying them for light switching duties. These usually have a pair of CAT D17000 engines for 400 bhp, and have four traction motors geared for around 35 mph maximum. OERM's 8580 is a 45 ton "drop-cab", which is a 44 tonner modified with a shorter cab and for closer clearances. This design was further modified with articulated trucks for narrow gauge (one each now at C&TS and Golden, plus many exports).

During WW2, GE had 65 ton and 80 ton centercab designs that had very different engines, frames and traction motors. After the war, GE introduced a new 65 and 80 ton that were marketed as separate models, but the only difference between them was the thickness of the deckplate. It seems that both 80 ton designs were produced for a while. There was also a 65 ton desing that looks like a GE 70 ton end-cab, but has a much smaller hood for a Cummins engine.

Many of the industrial loco builders seemed to offer the same standard sizes. The reason for the 44 ton is obvious, but it could be the 25, 45, 65 and 80 ton desings were common to all the builders to compete for US government contracts.

As if things weren't confusing enough, GE offered the 45 ton industrial loco with an extra 5 tons of ballast, making it a 50 ton. I have yet to figure out how to visually determine the difference, since this was a very common option. But this wasn't GE's "standard" 50 ton model; that was a centercab (using the same engines and main generators) on two axles for steel mill use. (Georgetown Loop's exCF&I loco is a latere variation of these, but actually was built lighter at 44 tons). Another common 50 ton model was a Caterpillar powered end-cab (Southern Pacific narrow gauge #1 and many more for export). The standard 35 ton (two axles, longer frame and bigger engine than a 25 ton, traction motors on both axles) was often ballasted to 40 and 50 tons. In the last years of the industrial line, GE offered an end-cab SL50 in both diesel-electric and electric third rail for transit, most ending up in New York.

Most industrial and export locomotives were rated at gross engine horsepower, whereas most larger locomotives are rated at the generator input or traction horsepower. For example, the 300 bhp 45 ton is only 260 traction hp. This has resurfaced with modern gen-set locomotives - a 2100 hp gen-set is only about 1950 traction hp, the rest of the hp going to radiator fans, air compressor and auxiliary power requirements.

When switching, the name of the game is tractive effort, and the more weight on the axles the more you can pull. But - horsepower is what gives you the ability to run with a train, limited by the gearing, truck design and thermal limits of the electrical equipment.