Dip stick tube size

[towacoman]

I have bought two different dip stick set ups for as 400 motor that I have.
The block is a early 1975. Can any body tell me what the diameter of the dip stick tube should be? They both seem to be to large to fit into my block. Thank you in advance

 

[melsg5]

Pontiac dip stick tubes consist of 2 sections one piece in the pan and the other on the outside of the block. Which piece are you talking about? I recommend you look at the firebird catalog at www.amesperf.com.