Do all 60,000 btu furnaces blow roughly the same CFM? Whether one is built in 2005 or in 2018?
Most 60,000 BTU models I see have a 3 ton blower for use with up to 3.5 ton AC's. Both PSC or ECM motors will have options to adjust airflow. Some 45,000 models come with 2 ton blowers. Once you get to 80,000 BTU models they offer versions with either 3 ton or 4 ton blowers.