that is actually a CCS (central cycle supply) chopper not a Bonanza, easily mistaken though :thumbsup: While I have never had one I did own its cousin a Manco Delta1 and am currently rebuilding what they all copied, a Bonanza. None of them used bushings in the headtube. I think the reasoning would be stress put on the frame at that point due to the rake, they probably figured a solid connection as they could would be best.
Most of the slop might actually come from both the headtube bolt and the holes in the fork trees for it. They will eat at each other over time and wobble out. What I usually end up having to do is to weld the hole up and re drill it out and sometimes have to get a new bolt if its hourglassed out enough. There's not much you can do with the headtube short of simply cutting it off and replacing if its really worn out of round though