You have a 350 as confirmed by the casting number. CKD is the engine to vehicle identification. In this case it means it came from a passenger car of some sort, hence the "C" which stands for Chevrolet, a requirement from GM which began in 1970 for all divisions. The KD part is a mystery to me, as the available blocks code in from of me are 1969 and earlier and KD is a code for a 396. If the engine came from a truck, your code should begin with a "T" but this practice changed sometime in the late 70s.