I'm pulling this from memory, so without looking at a picture, nor having worked on one in a while, take all this with a "grain of salt".
I assume you're talking about the post sticking up out of the top of the gov. hsng. That's a steel piece pressed into a soft metal hsng. On very early B's, it was solid. Very soon though they added an oil line to it to spray down on the gov.
As I recall, it's not uncommon for that post to work loose in the housing, with all the years of pressure on it from the throttle control. If you can't find a good used housing, you'll have to do, or get someone to do some work to get that tight in there again.