I've done a little research on the topic of CE blocks. My primary interest are CE blocks out of the Tonawanda BB plant. I own a 69 Z11 L34/M20 that I bought from the second owner who bought the car in 1970. A lady owner who used it for daily transportation
Car was original right down to the smog system. When I restored the motor I realized it had a CE block. I called owner number two and she said she did nothing to the car but drive it and change the oil. I contacted owner number one who I tracked down from the POP. He drove it for a year and traded it back in to the dealership. No engine problems with him either.