actually there is a difference between the carter of a cb550 and a cb 550f The first one takes 3.0liter the f has 3.2 oil capacity.
I find this information in my book ; (mine is a flemisch version) Honda 400&550 Fours Owners Workschop Manual ISBN 90 6127 107 X Copyright 1976 by J.H. Haunes& Company Ltd., Sparkford (England)