Napa has GL-4 in stock by the the gallon here in Colorado. It shouldn't hurt anything if it's GL-4. Just don't put GL-5 in the transmission or the transfer case. I put heavy duty GL-5 in all the other gearboxes myself.
Do you have a part/inventory number for the GL4/gallon? All the auto parts stores in this neck of the woods tell me it's unavailable. I stumbled upon this cache quite by accident.