I have not actually done this install, but I intended to a little while back. I did not do it because the '19 parts had poor availability and I wanted the bare minimum downtime as I rebuilt my transmission. I did research the difference between the two on the parts listings and it looks like it should be very doable and for reasonable cost. Part numbers that would need to be ordered:
Gear, Middle Driven B5H-17583-00-00
Gear, Middle Drive (23T) B5H-17582-00-00
Gear, First Pinion (15T) 2HC-17111-10-00
Gear, First Wheel (36T) 2HC-17211-10-00
Transfer Case B5H-17541-00-00
There is a thread on here that discusses this too, with one member saying he had accomplished it with just the gear changes and without changing the case. If the original case half can be used, then you avoid new bearings and associated seals or maybe you could just transfer those components to the new case as they are all the same part numbers. Maybe that member will respond to this thread. Total parts cost is around $220 for just the gears. Plus you'll likely want to move to bigger tires. Next time I split a case on either machine, I will make this mod. Hope this helps.