Black caps on hubs did not have a thing to do with the Adventure package or a luxury package with the off-road package. Sunroof was optional on all vehicles.
From the Hummer spec ordering book published by GM; prior to model year 2009, I still happen to have...
These are the items listed that make up an adventure package. The adventure package was one of three package available (in normal production they did produce a few unique packages from time-to-time, I have no info on those). The three unique package (which you could also refer to as models) were:
Base
Adventure
Luxury
You could also order a luxury package and include an off-road package that would add the same mechanical items as the adventure package. Needless to say, some times from an adventure would not be included on a luxury with the off-road package such as floor mats, they would remain the luxury floor mats.
Floormats, Oversized, carpeted, front
1 - Includes (B33) Floormats, Oversized, carpeted, rear.
Floormats, Oversized, carpeted, rear
1 - Included and only available with (B32) Floormats, Oversized, carpeted,
front.
Tires, LT285/75R16, on-/off-road, blackwall
1 - Included and only available with (ZM6) Suspension Package, off-road,
adventure.
Differential, full locking, rear, electronic driver selectable
1 - Included and only available with (ZM6) Suspension Package, off-road,
adventure.
Suspension Package, off-road, adventure, includes (G94) Differential,
full locking, rear, (QLB) Tires, LT285/75R16, on-/off-road, blackwall,
(NR6) Transfer case, 4:1 button actuated full time 4WD, 2-speed and
specially-tuned shocks
1 - Not available with (QB9) Wheels, 5 - 16" x 7.5" (40.6 cm x 19.1 cm)
chromed-aluminum.
Transfer case, 4:1 button actuated full time 4WD, 2-speed
1 - Included and only available with (ZM6) Suspension Package, off-road,
adventure.
Note, there is a few pages on what is standard and available for all models such as what models had power seats, etc.
Again this is an ordering spec book not engineering. Not even sure why I have it, but I do.
This is a copy of my 2008 H3 MSRP label. Noting a luxury package with an off-road package and what is in the off-road package.