You can probably get the doghouse cheapest from Paul at
www.myhumvee.com Good luck getting ahold of him though...
Parts: As far as the T-case goes, nobody that I know of offers it for sale directly on a website. I would talk to Travis about it and see what he says. Travis offers delivery and pickup with 250 miles of Ohio, You might be with in his range, or not need to drive very far to have your rig picked up and brought down there. Travis has lived and died by the H1, and is more then qualified to do the work.
I actually cant provide links from Rubber Duck. The web address does not change when you click on products. Go to
www.rubberduck4x4.com and they are all pretty easy to find. The cool head kit is listed under performance. The rock tubes will be in the exterior section. Halfshafts and diff centering kit are in driveline.