Tell us a little more about your project, and what you're trying to accomplish. Are you building a chopper or bobber, and want a small rudimentary drum for a clean looking front end, or are you buiding a old-school cafe racer or road racer replica and want a big, very functional drum brake with lots of stopping power?
I don't think typical Honda CL350, CJ360, CB/CL450 OEM wheels will be a direct bolt-on since the 550 fork tube spacing is wider. You might check out the CB400T Hawks. In any event, I believe you could mix and match axles and spacers to achieve a combination that will fit.