I assume that you are talking about the electric idle cutoff?? This is not actually a jet but is an electric valve that opens when the key is turned on. When the key is turned off, it shuts off fuel to the idle passages in the carb and (in theory) prevents “run on” after you turn the car off.
I disabled mine by lopping off the end and screwing it back into the hole. Works great. Now, I don’t need an electrical signal to “open up” the idle passages. And I have never had a problem with run on.
I would bet that a non electronic idle jet would simply be a bolt the same tpi as the original cutoff.