April 1969 was the END of the 1969 model year production, 1970 models would have been launched from middle of June to Middle of July.
I have seen cases where an engine is built up, found a defect, then had to be torn down and the good parts recycled and the bad ones thrown out. It happens all the time.
Like stated earlier, it's not worth arguing over. He has one of the prime years of the 340 engine to start with if it's all original.