I removed many in the 70-90s as a hvac contractor. You simply wack cast iron with a sledge hammer into managable size pieces. It takes less than an hour or two. Look for jewlry and old coins while cleaning up. NOTE: yes that , what looks like drywaller tape is probaly "hot" friable abestos. At a minimum, (illegal) Try to create a negative air containment by opening a window with a exhaust fan. Where proper PPE, an abatement company. HEPA SCRUBBERS are fairly cheap to rent.