If I SAS before a 6.0 swap it'll be with my current 4L60e, if its after it'll be 4L80e, the transfercase will most likely be NP241 if using a drivers drop axle or a NP205 w/ VSS installed if I use a pass. drop axle, I'll try to stay as close to factory option as possible.
The NP241 and NP243 are the exact same case other than the way they are shifted with the 243 obviously having the extra electrical parts.
My Z71 came stock with a 10 bolt and 3.73s but I pulled the 14 bolt SF off a 97 4x4 and it also had 3.73s. I believe unless special ordered most Z71s had 3.73s, and all 14SF's in 4x4's had 3.73s but I could be wrong. There is two easy ways to find out what gear ratio your truck came with, the first is to look in the glove box for the codes, I don't know those off hand or which one they are but many members on here do, the other is the place the rear of your truck on stands and spin your driveshaft till your driver side tire makes one complete rotation counting how many times you driveshaft turns. 3(3/4) turns is 3.73, 3(1/4) is 3.23, a little over 4 is 4.11, etc.