They have the same bolt pattern, but the offsets are different. GMC is 31mm, H2 is 18 mm. I can't remember exactly how offset works but I think the GMC wheel would tuck in further and you might start hitting suspension components. Others who look at this stuff more often can probably offer better opinions.
Usually I see the rims going the other direction - H2 wheels on other vehicles.
You may also want to define "stock" as there were probably several different wheel sizes with the different trim levels.