Correct, the B idle jet is threaded. Take a look here, the idle jet is on the bottom of the picture:
http://www.fordgarage.com/pages/jetflowrates.htm
It looks like your power jet tube is missing also. You can't buy them, but a piece of 1/8" diameter brass tubing can be substituted with a bit of modification to the upper casting. I replaced one just last week.
I can post some pictures of my B carb later today.