I was of the belief that the '77&'78 CB550K were very similiar, such as the '70-'76 models were.
Those look like "slip on" aftermarket mufflers, with the original (cut off) Honda headpipes. One muffler looks cracked in two? Mr Monkeyclaw seems to sell lots of beat up stuff. I think you can do better, I've bought vintage used slip-ons for less than [current $80 auction] & w/decent chrome.