Hey Steve-o. Bonjour. I think one of the best resources to plan such a trip would be the IAT.
Parc national de la Gaspesie, a national park, is administered by the province of Quebec, Sepaq, and that is a most important resource. Get your hands on the maps "Carte des sentiers et des services - 4 saisons" and "Carte topographique pour randonne pedestre et a skis" ... yep, they're in French but not hard to figure out.
It is a long drive but well worth it in my opinion. On the way, you may wish to hike the IAT over the high point in New Brunswick, Mt. Carlton, located in a provincial parc with good camping and cabin accommodations.