another transfer case question

[old Rusty C10]

truck is a 79. I believe I have the NP203 transfer case
truck is not going tonto any drive gear It will not shift into reverse or forward gears. At one point it was making a grinding gear noise now its not
with the rears in the air the driveshafts will move when you spin the tires both front and rear When you look under the truck it looks like the trans is going into gear when you pop it into reverse or drive yet there is no transfer or power from trans to wheels.... Am I correct in thinking that the chain between the sections int he transfer case has popped?

Also just for my own information, I am told there are different size output shafts that are between the trans and transfer case... if you have a mistmatched shaft/case , will they physically bolt up and allow the truck to move at all?
I was driving this truck somewhat locally for a few days not in 4wd. We were getting snow so I put the plow on and parked it started it up after snowing went to put in 4wd and plow truck wouldn't move.. this truck sits a lot and hasn't really moved far in several years,,, any ideas?