First, D264000 would probably have shipped in 1970.
The part you are referring to is the extractor rod, as it was called by S&W. It is commonly referred to as the "ejector" rod, which is certainly accurate as well.
By the time this gun was made, the extractor rod had left hand threads. Before about 1961, right hand threads were used on this model.
Edit: Be very careful when tightening this part. The treads are relatively fragile and over-tightening can easily result in stripped threads.