We have been looking into building a totally custom vehicle for a few years now and went through a lot of the research you are doing now. I can tell you that the best route is to forget about including any component of a Hummer (except possibly one) in your design as it is old technology and weak design by today's standards. Come up with a body/ chassis design you like and then use pre certified modules for each major area of the vehicle.
Axletech has full bolt in suspension modules that have EVERYTHING already assembled. You can get ctis, lockers, limited slip and portals if you want as well. They already designed geometry, differential, brakes, ctis, packaging etc. Just order and bolt directly to your chassis.
https://www.axletech.com/en/products/suspensions-modules/2000-isas
Engine: You can get a full engine package with CARB # from GM for the supercharged LSA
http://www.chevrolet.com/performance/crate-engines/e-rod-lsa.html
Wheels: Hutchinson DOT beadlocks
Lighting: Use either a factory assembly or an aftermarket DOT compliant option such as STARR etc and integrate into your body design
Windshield: If your design uses flat glass look at the heated windshields for H1 if you can find one as they are rare or design around another manufactures windshield
Dash: Either use an OEM option or I believe Haltech has a module that can connect to CAN and output via HDMI or VGA a fully custom displace to a LCD screen of your choice that you can embed into your dash like the new range rover sport dash cluster.
The devil is in the details with all of the little parts that make everything work such as interior lighting, power window assemblies, auto headlights etc and controlling everything via a custom BCM or other control system...
We gave up when we reached the body design and manufacturing point. Way too much $$ for small runs and then crash testing etc.