You can buy by pass filters with 13/16 inch thread.
If you want a remote base where the lines come in from the top, with a 1/2 inch pipe thread, here it is:
https://www.summitracing.com/parts/p...waAggxEALw_wcB
The answer was given already, the steel insert is molded into the aluminum housing, post #3. If it were threaded into the housing it would have an internal hex, or 4 sided internal drive recess, to tighten it into the housing.
As the conversation goes on, pertinent facts that weren't given in the initial question have been brought to light. I don't believe one here was trying to waste anyone's time, but telling the whole story up front would have been helpful.