Not in my product range, but sourcing for customer as an extra services is what we had been done, I'm not really know about tractor like Cummins 4BT, so just copy some fact from wikipedia as below.
The Cummins B Series is a family of straight-four and straight-6 diesel truck and industrial piston engines manufactured by Cummins. The B Series is known for displacing "one liter per cylinder" because of the popular 3.9 litres (238.0 cu in) straight-four and 5.9 litres (360.0 cu in) straight-six. A 3.3 litres (201.4 cu in) straight-four is also available. The B Series is widely used in many segments, including pickup trucks (the Dodge Ram), buses, military vehicles, construction equipment, and marine. Some of the construction and marine applications have actually featured two B series Cummins engines.
The engine was originally designed by Cummins and Case Corporation for commercial truck applications, and appeared in a light-duty truck, the Dodge Ram, in 1989. This was not the first engine to appear in Dodges as a Diesel option. Mid-1970s D models offered the rare, underpowered, Mitsubishi non-turbo diesel.
Every Cummins powered Dodge Pickup (since initial production in 1989) has come equipped with a turbocharger. It uses a gear-drive camshaft for extra reliability. Also specified is a deep-skirt engine block and extremely strong connecting rods. A Holset turbocharger is used. The original B Series was updated with 24 valves and an electronic engine management system to become the ISB in 1998.
The 3.9L/4BT Cummins is an engine in the same family as the 5.9 litres (360.0 cu in) Cummins turbodiesels. The 3.9L/4B is an inline four cylinder turbodiesel that was popular for many step van applications, including bread vans and other commercial vehicles. This engine is also used in various industrial, construction and agricultural applications. With a cylinder bore of 4.02 inches (102.1 mm) and a piston stroke of 4.72 inches (119.9 mm), the engine had a wet weight of 745 pounds (338 kg). In recent years it produced 130 horsepower (97 kW; 132 PS) and 355 pound-feet (481 N·m) of torque. The 4BT today is also popular as a conversion engine among many light-duty pickup trucks that were originally equipped with gasoline engines. This is due to its high fuel efficiency while producing power comparable to the original light-duty gasoline engine. The 4BT engines have the same pistons, connecting rods, valvetrain components, and injectors as their 6BT counterparts.