If you are planning on using a 6.2 than I can't believe it would blow up a transfer case without dumping a ton of money in it. They aren't power houses in stock form. The bell housing is the same as a sbc/bbc which should be the same as your 8.1. Have you looked into how you will affix flanges to the shafts on the tcase to install drive shafts or couplers yet? You might be able to get a drop box from SCS and you can change the gears out easily in those.

And no, you do not need the chain in the tcase for it to operate. Popular GM RH drop transfer cases are np208's and np241's.