You can find the Hummer EV configurator directly on the GMC website https://www.gmc.com/trucks/hummer/pickup/build-and-price/
It's pretty cool to mess around with and see what you can come up with.
It looks like the Hummer EV has a battery around 170kWh, but we don't know the exact usable capacity yet. It should get around 250-300 miles of range. We'll have to wait for official numbers from GMC.