The original carburetor on a 1981 Dodge pickup with a 318 engine was most likely a
Rochester Quadrajet. However, there's a slight chance it could have been a Motorcraft depending on the specific trim level and options. The Rochester was far more common.
To be absolutely certain, you'd need to check the vehicle's original paperwork, the casting number on the carburetor itself (if it's still original), or a parts catalog specific to that year and model truck.
