Are you sure about that width? My parents have an Envoy (same thing, only a GMC), plus I've serviced many of those over the years, the axle is definitely wider than 60".
The offset of the pinion won't be a major issue, it's actually quite common on most rear ends. Only way I could see an issue is if it was an extreme offset, like the axle from an Astro van. A bigger problem is going to be finding wheels, as the trailblazer has a small 6 lug pattern not shared with any other GM vehicle.
