The seat in Jevfro's pic is definitely NOT an OEM CB400F or CB350F seat. Neither of those models had the owner's manual holder on the underside of the seat pan. My '76 550K does have the owner's manual holder similar to Jev's seat, but the pan shape is different in several regards. I have no idea what seat is shown in Jev's pic, but looking at the hinge bracket mount spacing I can tell you for a fact that it is not a direct bolt-on to a 350F.