I would not be surprised. If it's the new body style, then it most likly has the governor in it. I've got one of the old body styles, and I'm sure I could get it to 100 (if there was some place I could do it safely). My oldsmobile only goes to 80 on the dash, and I've buried the needle once before, so the high limit on the speedometer does not always equal the high limit of the car.
That 4.3l engine rocks. Powerful, and efficent. My s10 gets 25mpg consistantly. It's not uncommon for it to get better mileage then my 89 oldsmobile w/ a 4 cylinder