Main case 1
There's a gasket between the 2 case halves, which doesn't get seated until you actually bolt this assembly to the transfer case.
Dress the gasket and install the rear cover/bearing/shift mechanism into the main housing.
The 1/4" bolts just secure the rear cover until the main bolts are installed.
TAKE NOTE: you may want to replace the factory 1/4" hex bolts w/allen bolts. See the next steps for the reason.