They have the offset holes for a high port style head the only real issue other than replacing the flanges is the actual height of the header. They are made to sit at a different level because the ports are raised. You could try and see, I’d just get a set of tri-y style if it was me my dad’s friend had a set mint off his 67 vert let me ask him. He went to a bigger header with his 347 but the tri-y worked awesome with his built up 289.