263hd and 263xhd

hello,
first post here.i hope it's in the right place,and i don't offend anyone.after searching the web this site has come up a few times.this weekend i am going to attempt an engine/transmission swap.2001 silverado 6.0/4l80e trans with a 263hd transfer case.i have a complet 8.1 with an allison 5spd.does anyone know if the transfer cases will interchange?i have a 263hd,but i think the allison has the 263xhd.the rpo codes are the same in both trucks np1.
thanks for any help i can get

never got any replies,but maybe this will help someone in the future.the transfer cases are not interchangeable.spline differences on both input and output shafts.i did finish this job.went from a 6.0/4l80e trans to an 8.1/allison 5spd.works great.

Wow that's awesome. Any pics? How does the 8.1 compare to the 6.0?