Hi pj. Welcome to iboats. Great to have another AT owner here in the forums. Mine was a '59ish aluminum DUT-14 runabout/skiboat that I have converted to an aluminum, tiller drive, flats boat sort of thing. As far as replacing the gunnels, I would start by removing the old ones while keeping them as intact as possible so that you can use them as templates later. You'll then need to find wood to replace them with. There are several options depending on your budget, but oak should be readily available, looks great, has good strength and can be steamed and bent with ease, if need be. We actually have another forum member who just did a similar job. I'll see if I can find the thread. In the meantime check out the link below for a bit more info on your boat. Perhaps it will help you pin down the exact make and model.
Arkansas traveler - Classic Boat Library (aluminum)
Arkansas traveler - Classic Boat Library (fiberglass)