08 5-cly. models will have an aluminum front diff case...adventure or not. Also no front locker in 08. Some 08 Alpha’s had cast iron cases...I’ve seen them both ways. Although you can install a locker in an alum case, I’ve never seen one come that way from the factory. I have seen cast iron cases on 09-up 5-cly. H3’s, both Adv Pak and base.
The GM 8.6 rear axle got a larger inner pinion bearing in 09. Not sure it’s really that big of a deal but the 09-up models do have this. They look identical from the outside but, they take a different bearing kit. This is true for other 09-up GM 8.6 equipped trucks as well.
5-cly. axles are definitely more desirable, (if only for the lower gearing). Lots of Alpha owners regear to 4.56 but swapping the entire f&r axles is often cheaper and easier than a regear.
Adv Pak t-case is a very worthwhile swap if you are a wheeler...especially if you run 35” tires. Also, the difference between the t-case ratios is only in low range...the two share identical gearing in high range. All cases from all years and models interchange but, the Alpha cases are slightly different for the V8 exhaust system. If you install a 5-cly t-case in an Alpha, be prepared to do some minor grinding or put some small dents in the crossover pipe.
