CNG/Propane Gaseous Engine Prep Package (The CNG/Propane Gaseous Engine Prep Package for power conversion to compressed natural gas (CNG) or propane autogas is available at time of order. Included are hardened engine intake valves, exhaust valves and valve seats. Available with 6.8L V10 gas engine. Vehicle will be equipped with the standard factory gasoline fuel system. This package does not include compressed natural gas/propane fuel tanks, lines, etc.