Look in tom endy's restoration tips.
http://www.santaanitaas.org/wp-conte...etor-11-07.pdf
There were three different secondary wells, I believe, only the third style is available.
The well gets screwed in and typically several threads of the casting are exposed when it is properly installed.
However, the well can block the comp jet channel. I modify the well with a file to correct this problem.
I think Endy covers this.