Welcome from sunny but chilly southern Arizona!
Avoid parts from 4-into-1, ask before purchasing stuff on various suppliers... and Honda control cables are excellent and superior to aftermarket. Order from South Sound Honda of Olympia WA for good prices on OEM parts at discount and reasonable shipping charges.
74-76 cb550 have wear issue in rocker arm cover where you get eccentric wear in the cover from the rocker shafts, this makes it impossible to get consistent valve lash with wear and destroys cam and rocker arms along with the cover, that the one weakness,... other than brake performance being typical 70s Honda. The 77-78 top cover pinned the shafts eliminating this issue. Just be aware, easy to check for this wear...
Congrats on purchase, 550s are a great bike...more fun because of the nimble handling. Nice original examples are getting rarer, so glad you are keeping it original.