This manual covers the 1977 Chevrolet Medium Duty Truck models: P40 Forward Control Chassis, S60 School Bus, C & M 50-65 series M.D. steel conventional cab, and T60-65 M.D. steel tilt cab. If you have a 1978 or 1979 Chevrolet medium duty, you'll need this book plus the supplement for your year. This book can be used to repair GMC trucks as well as Chevrolets.