So Ben brings some good points to the table.
The LS swaps normally go as an engine / trans unit. Old in. New out. This is good and easy as it ensures a matched tranny. With the 6.0 or 6.2, will come the HD 6speed 80 or 90 auto. Usually the 90 if I recall. Good stuff.
This brings out the potential need for a tcase adapter and driveshaft changes. See? Nothing is easy.
Even when it is.
Cooling comments are right on too. And the large LS swaps usually take the radiator from the donor vehicle as well. Otherwise premium custom rads get expensive fast.
:-)