I did some research and discovered the differences between the 918F, IT18F, 924F, and IT24F. Hope it'll help anyone who may buy one of these models in the future.
The 918F is the weakest of the machines, with a 98 hp and a smaller 11" torque converter. The IT18F is more powerful, with a 105 hp engine, 13" torque converter, and a parallel lift linkage that also provides more breakout force and lift height than the conventional Z-Bar of the 918F.
The 924F is the 918F with the IT18F's stronger engine and torque converter. The IT24F is nearly the same as the IT18F. Both the 924F and IT24F also received a new higher flow hydraulic pump, pilot controls (as opposed to the direct linkage to the valves in the *18F models), a higher relief valve pressure, and transparent joints between the 3 panels of the front windshield for improved visibility.
I'll probably post pictures of my new toy next week.