* Engine: The size and type of engine (e.g., 318, 360) drastically affected towing capacity. Larger engines meant higher capacity.
* Axle Ratio: Higher numerical axle ratios (e.g., 3.54 vs. 2.73) allowed for greater towing ability.
* Transmission: Automatic transmissions generally allowed for higher towing capacities than manual transmissions.
* GVWR (Gross Vehicle Weight Rating): This is the maximum weight of the van itself plus its contents. A higher GVWR meant more capacity to tow.
* Specific Model Options: Some options may have altered the structural integrity or weight distribution, influencing towing capacity.
Therefore, you cannot find a single definitive answer without knowing the exact specifications of the particular 1981 Dodge 350 Custom van. To determine the towing capacity, you would need to locate either:
* The original owner's manual: This is the best source.
* The vehicle's sticker: Sometimes a sticker indicating towing capacity is located inside the driver's side door jamb or elsewhere.
* A Dodge parts/service manual from that year: This may list the capacity for various configurations.
Without this information, any answer would be purely speculation and potentially unsafe. Trying to tow more than the van is rated for is extremely dangerous.
