Vaughn runs a 436 cubic inch Ford Performance / Roush Yates racing engine with around 900 HP and 750 lb/ft torque. The engine is based on a Sprint Car engine but has greater displacement to produce more torque for the demands of drifting.
The Mustang has the usual exquisite engineering and workmanship we have come to expect from Vaughn's team. The unibody has been cut back to the limits of FD rules and replaced with a tube frame. Aluminum bash bars bolt to the tubular substructure. This is strong and light. The rear of the car contains the fuel cell and rear mounted radiator. There is a lot of cool secret stuff we could not see.
The Ford engine uses a belt drive for the cam getting rid of the stock chain. This takes some harmonic stress off the valvetrain. The engine sits in a sweet CNC machined motor plate instead of conventional motor mounts and is used as a stressed member. The motor plate also serves as a mount for the alternator, dry sump and power steering. This is really cool packaging.
The Roush Yates engine uses individual throttle body injection. ITB's give the best throttle response and allow great breathing. The ITB's are like Hilborn Mechanical Injection or downdraft Weber carburetors from cars of old but with electronic injectors.
You can see some of the details of the motor plate and drysump drive here.