There is no reported drug interaction between Goody’s Headache Powder and gabapentin.
Goody's Headache Powder contains aspirin, acetaminophen, and caffeine. The amount of each ingredient varies based on the particular type of Goody’s Powder, but the Extra Strength contains 260 mg of acetaminophen, 520 mg of aspirin, and 32.5 mg of caffeine. Aspirin and acetaminophen have similar mechanisms that block COX-mediated pain. Caffeine causes constriction of blood vessels surrounding your brain which decreases blood flow and therefore headache related tension.
Gabapentin is used for a variety of indications including neuropathic pain and seizures. It is structurally and mechanistically different than the ingredients in Goody's Headache Powder. Taking both at the same time should not cause issues based on the information available.