Any of the following would meet your needs. And, yes, there's a common thread here. Two seats bolted in the back. Because there's not any four-door old small pickups.
2.2L Mazda/Perkins engine:
1983-1984 Ford Ranger 2.2 diesel with two seats bolted in the back
1983-1986 Mazda B2200 diesel with two seats bolted in the back
2.3L Mitsubishi turbo engine:
1983-1986 Dodge Ram 50 turbodiesel with two seats bolted in the back
1983-1986 Mitsubishi Mighty Max turbodiesel with two seats bolted in the back
1985-1986 Ford Ranger turbodiesel with two seats bolted in the back
2.2L Isuzu engine:
1981 Chevy LUV diesel with two seats bolted in the back
1981-1986? Isuzu P'up with two seats bolted in the back
1982-1986 Chevy S-10 diesel with two seats bolted in the back
2.2L Toyota engine:
1981-1984? Toyota Truck diesel with two seats bolted in the back
2.4L Toyota engine:
1985?-1987 (counting Canada) Toyota Truck diesel with two seats bolted in the back
2.4L Toyota turbo engine:
1985?-1987 (counting Canada) Toyota Truck turbodiesel with two seats bolted in the back