The VC-25B is powered by GE CF6-80C2B1 turbofan engines. They were not developed until the 1970s and are more efficient than the original turbofan engines.
The "Beast", as it is known by the USSS, is a cobbled together Cadillac limousine body on a GM Kodiak medium duty truck chassis and is powered by a twin turbo Diesel engine. It gets about 7 to 8 MPG. It uses headlights from the Escalade, taillights from the discontinued STS, and barely resembles a Cadillac. It, along with a second limo and a USSS Suburban are flown about on a C-17 that is specifically tasked for their movement.
GM builds another such limo every 4 years and the current model goes to the VP or the USSS fleet to haul around visiting heads of state or for training purposes.