The owner of this Big Bud 450/50 tractor set out to replace the motor. They swapped to a 27.0 L Caterpillar 3412 V12 that was previously being used at a hospital as a backup generator. To fit this beast of a motor, they had to extend the frame 22 inches and raise the cab eight inches. The video description states the V12 made 800 horsepower and 2700 lb-ft of torque on the dyno.
Source: Sean Bronec via BangShift