The 1981 Dodge Ram doesn't use a 318 in a minivan configuration. The Ramcharger and other trucks used the 318, but minivans of that era (Dodge Caravan/Plymouth Voyager) used the slant-six (225 cubic inch) engine or a smaller V8 (like a 3.7L, depending on the year). There were no 318 V8 minivans from Dodge in 1981.
Therefore, there's no firing order for a "1981 Dodge Ram 318 minivan" because that vehicle didn't exist. You'll need to specify the correct engine for the vehicle to get the firing order.
