After 1965, Most all of the Heavy Duty 1966 Chevrolet trucks, came standard with the 366ci., big block, not the same block, as the old 348, & 409's. My '65 Chevy L80 Wrecker, had a 409ci. big block, & my '60 Chevy L80 Roadtractor, had a 348ci. big block, in it.
