Most people who get into lifting their H1's are going with a combination of 2" body lift and 2" suspension lift; if you plan to go no larger than 39.5" you don't necessarily need both; a 2" body lift will clear the tires with ease, and is relatively inexpensive.
Here's an article I wrote about the Rubberduck 4x4 suspension lift; it is not the cheapest option, but I have been happy with it:
http://hummer.off-road.com/hummer/ar....jsp?id=330715
There are mixed opinions about the "spring spacers only" vs. a complete suspension lift. Email me privately if you have specific questions, I will happily answer your questions as time allows.
FWIW, I think the Detroit is a great choice for rear locker, but some people don't like them as much on the road as the selectable Auburn E-lockers, especially in snow and ice. Again, I would be happy to share my personal opinions on this in greater detail if you have specific questions, but much of it depends on what your primary use of the truck is going to be.