Guy Martin set a new British top speed record of 103.6 mph in a custom JCB Fastrac at Elvington Airfield in Elvington, UK. The tractor was built on a weight-reduced 4000-series Fastrac chassis with an aerodynamic body designed by Williams Advanced Engineering. They replaced the factory AGCO SISU diesel engine with a 7.2 L JCB Dieselmax inline-six featuring stronger connecting rods, upgraded fuel system, larger injectors, and piston cooling. The engine is capable of 1,000 horsepower and 2,500 lb-ft of torque however Farmers Weekly reports they reduced output by a half for the record run. They also replaced the factory AGCO CVT transmission with a ZF six-speed manual transmission from heavy-duty truck with a multi-plate wet clutch.
Source: @JCBMachines and Farmers Weekly via Jalopnik