GE made a variety of 24" gauge locos. The HM and GHM series of traction motors are from GE's (Gear) Hoist and Mining section. The HM/GHM motors and gear units can be found in stock GE models, just as the GE car and locomotive designs can show up in the mining line.

My question on the 23 tonners are how the traction motors are mounted - Wheelbarrow axle-hung? Gear unit either parallel or hypoid and single/double/triple reduction?

> The GE on the Kauai Plantation Railway is the usual two-axle type, but it does seem narrower than normal.
Correct - it was a stock 36" gauge GE 25 ton (8' wide) that was cut down to be narrower by the second steel mill it was assigned.

One of (if not the biggest and most powerful) 24" gauge diesel-electrics I am aware of at 51 tons and 640 horspower, and capable of three in mu! [en.wikipedia.org] (I normally don't care for Wikipedia, but this is actually a good and fairly accurate article.)