[MrBeast]

there is a very good chance that it has a 4.10 ratio rear, and the tranny is either a TH350 or a TH400 the easiest way to tell is the TH400 has a pan that looks like a sail boat, the th350 has a pan that is square with a triangle missing from one corner.

If it is a manual the transmission will be a SM465, and the Tcase will most likely be a NP205, if it is an auto the Tcase can also be a 205, but it could also very well be a NP203, they put both in, the way to tell is to look at the shift boot, if it says 4 hi, 4low and then says lock at each end, with a neutral in the middle, that is a NP203, the 205 is idenitified by the fact that it is a gear driven transfer case and it can be difficult to shift.

The 205 case is heavy made out of solid cast iron, and will have a PTO port on it.

IF you cant figure it out, post some pics and I will let you know what you have.

Being a K-20 it has a 10 bolt front axle up front, and the rear will most likely be a 14 bolt, but in the 3/4 tons they put both semi and full floaters in em, the easiest way to tell is weather or not the yoke carrier bolts into the front of the pumpkin, if there are no bolts around it, it is a semi floater.

But really post some pics is your best bet at getting things identified.