getting ready to assemble my motor ('69 350), I notice there is a small soft plug about 1/2 in dia , where does it go ? I don't recall taking one out like it out before it went to the machine shop????????thanks

 

Pictures might help with this one...

All I can think of is a vacuum port cap.

 

The one in the back of the engine with that famous oil gallery plug with the hole in it behind it is bigger than that isn't it?

 

that plug is about 3/4. this is 1/2'' OD looks like a regular soft plug