Mine is a 22 HP like in my previous description of 224. That means 22HP, 4WD. A 284 would be 28HP,4WD, etc.
Like I said, they ain't small tractors. Northern only sells assembled units to my knowledge. The NT 204 (20HP, 4WD) is a little shorter than mine,not much though, and has smaller tires. It is a tad smaller but not a lot.
I got mine as a crate unit from a dealer and assembled myself. Dealers sometimes sell as crate form but mostly assembled.